■cS 


VIOL 


LIBRARY 

OF  THE 

University  of  California. 

BIOLOGY              r, 
LIBRARY                <-"«>S 

FIRST    COURSE    IN    BIOLOGY 


fiEKEHAL 


■?&&&■ 


THE   MACMILLAN  COMPANY 

NEW  YORK    •    BOSTON   •    CHICAGO 
ATLANTA   •    SAN   FRANCISCO 

MACMILLAN  &   CO.,  Limited 

LONDON   •    BOMBAY   •    CALCUTTA 
MELBOURNE 

THE  MACMILLAN  CO.  OF  CANADA,  Ltd. 

TORONTO 


FIRST  COURSE  IN  BIOLOGY 


BY 

L.    H.    BAILEY 

PART  I.     PLANT  BIOLOGY 


WALTER    M.    COLEMAN 

PART  II.    ANIMAL    BIOLOGY 
PART  III.    HUMAN  BIOLOGY 


Nrtn  gork 
THE   MACMILLAN    COMPANY 

1909 

All  rights  reserved 


BIOLOGY 

LIBRARY 

6 


GENERAL 


Copyright,  1908, 
By  THE   MACMILLAN   COMPANY. 


Set  up  and  electrotyped.      Published  July,  1908.      Reprinted 
October,  1908;  February,  September,  1909. 


KottoooS  $rrS3 

J.  S.  Crashing  Co.  —  Berwick  &  Smith  Co. 

Norwood,  Mass.,  U.S.A. 


OF  THE 

DIVERSITY.  1 1 

PREFACE 

The  present  tendency  in  secondary  education  is  away 
from  the  formal  technical  completion  of  separate  subjects 
and  toward  the  developing  of  a  workable  training  in  the 
activities  that  relate  the  pupil  to  his  own  life.  In  the 
natural  science  field,  the  tendency  is  to  attach  less  im- 
portance to  botany  and  zoology  and  physiology  as  such, 
and  to  lay  greater  stress  on  the  processes  and  adaptations 
of  life  as  expressed  in  plants  and  animals  and  men.  This 
tendency  is  a  revolt  against  the  laboratory  method  and 
research  method  of  the  college  as  it  has  been  impressed 
into  the  common  schools,  for  it  is  not  uncommon  for  the 
pupil  to  study  botany  without  really  knowing  plants,  or 
physiology  without  knowing  himself.  Education  that  is 
not  applicable,  that  does  not  put  the  pupil  into  touch  with 
the  living  knowledge  and  the  affairs  of  his  time,  may  be 
of  less  educative  value  than  the  learning  of  a  trade  in  a 
shop.  We  are  coming  to  learn  that  the  ideals  and  the 
abilities  should  be  developed  out  of  the  common  surround- 
ings and  affairs  of  life  rather  than  imposed  on  the  pupil 
as  a  matter  of  abstract,  unrelated  theory. 

One  of  the  marks  of  this  new  tendency  in  education  i 
is  the  introduction  of  unit  courses  in  biology  in  the  sec-  - 
ondary  schools,  in  the  place  of  the  formal  and  often  dry 
and  nearly  meaningless  isolated  courses  in  botany,  zoology, 
and  physiology.     This  result  is  one  of  the  outcomes  of  the 
recent   nature-study   discussions. 

The  present  volume  is  an  effort  to  meet  the  need  for 

19Q75;5 


vi  PREFACE 

a  simple  and  untechnical  text  to  cover  this  secondary 
biology  in  its  elementary  phases.  The  book  stands  be- 
tween the  unorganized  nature-study  of  the  intermediate 
grades  and  the  formal  science  of  the  more  advanced 
courses.  It  is  a  difficult  space  to  bridge,  partly  because 
the  subjects  are  so  diverse,  and  partly  because  some 
teachers  do  not  yet  understand  the  importance  of  im- 
parting to  beginners  a  general  rather  than  a  special 
view  point. 

Still  another  difficulty  is  the  lack  of  uniformity  in  the 
practice  of  different  schools.  It  is  not  urged  that  it  is 
desirable  to  have  uniformity  in  all  respects,  but  the  lack 
of  it  makes  it  difficult  to  prepare  a  book  that  shall  equally 
meet  all  needs.  It  is  hoped,  however,  that  the  present 
book  is  fairly  adaptable  to  a  variety  of  conditions,  and 
with  this  thought  in  mind  the  following  suggestions  are 
made  as  to  its  use  : 

Being  in  three  separate  parts,  the  teacher  may  begin 
with  plants,  or  with  animals,  or  with  human  physiology. 

If  a  one-year  course  is  desired,  the  topics  that  are 
printed  in  large  type  in  Parts  II  and  III  may  be  used, 
and  a  choice  from  the  chapters  in  Part  I. 

For  three  half-year  courses,  all  the  parts  may  be  cov- 
ered in  full. 

If  the  course  in  biology  begins  in  the  fall  (with  the 
school  year),  it  may  be  well  to  study  plant  biology  two 
days  in  the  week  and  animal  biology  three  days  until 
midwinter;  when  outdoor  material  becomes  scarce,  human 
biology  may  be  followed  five  days  in  the  week ;  in  spring, 
plants  may  be  studied  three  days  and  animals  two  days. 

If  the  use  of  the  book  is  begun  at  midyear,  it  will  prob- 
ably be  better  to  follow  the  order  in  the  book  consecu- 
tively. 


PREFACE  vii 

If  it  is  desired  to  take  only  a  part  of  the  plant  biology, 
Chapters  VI,  XIV,  XX,  XXIII,  XXIV  may  be  omitted, 
and  also  perhaps  parts  of  other  chapters  (as  of  X,  XII, 
XIII)  if  the  time  is  very  short.  The  important  point  is 
to  give  the  pupil  a  rational  conception  of  what  plants  are 
and  of  their  main  activities ;  therefore,  the  parts  that  deal 
with  the  underlying  life  processes  and  the  relation  of  the 
plant  to  its  surroundings  should  not  be  omitted. 

If  more  work  is  wanted  it  is  best  to  provide  the  extra 
work  by  means  of  the  study  of  a  greater  abundance  of 
specimens  rather  than  by  the  addition  of  more  texts;  but"" 
the  teacher  must  be  careful  not  to  introduce  too   much 
detail  until  the  general  subject  has  first  been  covered. 

The  value  of  biology  study  lies  in  the  work  with  the 
actual  things  themselves.  It  is  not  possible  to  provide 
specimens  for  every  point  in  the  work,  nor  is  it  always 
desirable  to  do  so ;  for  the  beginning  pupil  may  not  be 
able  to  interest  himself  in  the  objects,  and  he  may  become  ( 
immersed  in  details  before  he  has  arrived  at  any  general 
view  or  reason  of  the  subject.  Great  care  must  be  exer- 
cised that  the  pupil  is  not  swamped.  Mere  book  work  or  i 
memory  stuffing  is  useless,  and  it  may  dwarf  or  divert 
the  sympathies  of  active  young  minds. 

Every  effort  should  be  made  to  apply  the  lessons  to 
daily  life.  The  very  reason  for  knowing  plants  and  ani- 
mals is  that  one  may  live  with  them,  and  the  reason  for 
knowing  oneself  is  that  he  may  live  his  daily  life  with 
some  degree  of  intelligence.  The  teacher  should  not  be 
afraid  to  make  all  teaching  useful  and  practical. 

In  many  cases  a  state  syllabus  designates  just  what 
subjects  shall  be  covered ;  the  topics  may  be  chosen  easilv 
from  the  text,  and  the  order  of  them  is  usually  left  largely 
to  the  discretion  of  the  teacher. 


Vlii  PREFACE 

Finally,  let  it  be  repeated  that  it  is  much  better  for  the 
beginning  pupil  to  acquire  a  real  conception  of  a  few 
central  principles  and  points  of  view  respecting  common 
forms  that  will  enable  him  to  tie  his  knowledge  together 
and  organize  it  and  apply  it,  than  to  familiarize  himself 
with  any  number  of  mere  facts  about  the  lower  forms  of 
life  which,  at  the  best,  he  can  know  only  indirectly  and 
remotely.  If  the  pupil  wishes  to  go  farther  in  later  years, 
he  may  then  take  up  special  groups  and  phases. 


CONTENTS 


General  Introduction 

PART    I.     PLANT    BIOLOGY 

CHAPTER 

I.  No  Two  Plants  or  Parts  are  Alike 

II.  The  Struggle  to  Live 

III.  Survival  of  the  Fit 

IV.  Plant  Societies 
V.  The  Plant  Body 

JVL-  Seeds  and  Germination 

VII.  The  Root— The  Forms  of  Roots 

VIII.  The  Root  —  Function  and  Structure 

IX.  The  Stem  —  Kinds  and  Forms  —  Pruning 

X<  The  Stem  —  Its  General  Structure 

XI.  Leaves  —  Form  and  Position    . 

X-H>.  Leaves  —  Structure  and  Anatomy 

XHJ.  Leaves  —  Function  or  Work 

_X-fvv.  Dependent  Plants     . 

XV.  Winter  and  Dormant  Buds 

XVI.  Bud  Propagation 

XVII.  How  Plants  Climb     . 

XVIII.  The  Flower  —  Its  Parts  and  Forms 

XIX.  The  Flower  —  Fertilization  and  Pollination 

,2Q£«.  Flower-clusters 

XXI.  Fruits  .... 

XXII.  Dispersal  of  Seeds   . 

XXM.  Phenogams  and  Cryptogams 
XXLVr"  Studies  in  Cryptogams 


PAGE 

xi 


CONTENTS 


PART    II.     ANIMAL   BIOLOGY 

CHAPTER  pAGE 

I.     Introduction j 

II.     Protozoans IO 

III.     Sponges  .... 


17 

IV.  Polyps 22 

V.  ECHINODERMS -,, 

VI.  Worms ,2 

VII.  Crustaceans 5I 

VIII.  Insects g, 

IX.  Mollusks g7 

X.  Fishes IOg 

XI.  Batrachians I26 

XII.  Reptiles I3o 

XIII.  Birds !r0 

XIV.  Mammals ^^ 

PART    III.     HUMAN    BIOLOGY 

I.  Introduction ! 

II.  The  Skin  and  Kidneys 16 

III.  The  Skeleton 29 

IV.  The  Muscles ,g 

V.  The  Circulation  .        .        .        .        .        .        .        .51 

VI.  The  Respiration yQ 

VII.  Food  and  Digestion 89 

VIII.  The  Nervous  System n7 

IX.  The  Senses I42 

X.  Bacteria  and  Sanitation 158 

General  Index         i 


GENERAL   INTRODUCTION 

PRELIMINARY   EXPERIMENTS 

These  experiments  are  inserted  for  those  pupils  who  have  not 
had  instruction  in  chemistry  and  physics,  to  give  them  a  point  of 
view  on  the  subjects  that  follow.  At  least  a  general  understanding 
of  some  of  these  subjects  is  necessary  to  a  satisfactory  elementary 
study  of  biology. 

Elements  and  Compounds.  —  The  material  world  is  made 
up  of  elements  and  compounds.  An  element  is  a  sub- 
stance that  cannot  be  separated  into  two  or  more  sub- 
stances. A  compound  is  formed  by  the  union  of  two  or 
more  elements.  All  the  material  or  substance  of  which 
the  earth  and  its  inhabitants  is  composed  is  formed  of  the 
chemical  elements ;  this  substance  taken  all  together  is 
known  as  matter. 

Carbon  and  iron  are  examples  of  elements.  Compare  a 
bit  of  charcoal,  which  is  one  form  of  carbon,  with  a  new 
iron  nail.  Which  is  brighter  ?  Heavier  for  its  size  ? 
Tougher  ?  More  brittle  ?  Harder  ?  More  readily  com- 
bustible ?  Resistant  to  change  when  left  exposed  to  air 
and  dampness  ?  There  are  two  other  forms  of  carbon  : 
graphite  or  black  lead  (used  in  pencils  and  stove  polish); 
and  diamond,  which  occurs  in  crystals  and  is  the  hardest 
known  substance.  Iron  does  not  have  varied  forms  like 
carbon.  Sulfur  is  another  element.  What  is  its  color? 
Has  it  odor?  Taste?  Will  it  dissolve  in  water?  Is  it 
heavy  or  light  ?  Will  it  burn  ?  What  is  the  color  of 
the  flame  ?     Of  the  fumes  ?    Phosphorus,  another  element, 


Xll  GENERAL   INTRODUCTION 

burns  so  readily  that  it  ignites  by  friction  and  is  used  in 
matches.  Rub  the  tip  of  a  match  with  the  finger.  What 
is  the  odor  of  phosphorus  ?  Phosphorus  exists  in  nature 
only  in  combination  with  other  elements.  Lead,  tin,  silver, 
gold,  copper,  zinc,  nickel,  platinum,  are  elements. 

There  are  less  than  eighty  known  elements  ;  but  the  com- 
pounds formed  of  them  are  innumerable.  Carbon  is  found 
in  all  substances  formed  by  the  growth  of  living  things. 
That  there  is  carbon  in  sugar,  for  example,  can  easily  be 
shown  by  charring  it  on  a  hot  shovel  or  a  stove  until  its 
water  is  driven  off  and  only  charcoal  is  left.  Part  of  the 
starch  in  a  biscuit  remains  as  charcoal  when  it  has  been 
half  burned. 

Oxygen  and  the  Air.  —The  great  activity  of  pure  oxygen 
in  attacking  other  substances  can  be  shown  by  passing 
into  a  fruit-jar  a  lighted  splinter,  a  piece  of  lighted  mag- 
nesium ribbon,  an  old  watch  spring  (or  a  bit  of  picture 
wire),  the  end  of  which  has  been  dipped  in  sulfur  and 
lighted.  About  one  fifth  of  the  air  is  oxygen  and  about 
four  fifths  is  nitrogen  and  other  inactive  gases.  Pure 
nitrogen  will  quickly  extinguish  a  lighted  splinter  thrust 
into  it.  It  is  the  oxygen  in  the  air  that  supports  all  forms 
of  burning.  Less  than  one  half  of  one  per  cent  of  the 
air  is  an  inactive  gas  called  carbon  dioxid,  a  compound 
of  carbon  and  oxygen.  It  is  formed  not  only  when  wood 
or  coal  is  burned,  but  also  by  the  life  processes  of  animals 
and  plants. 

Favorable  and  Unfavorable  Conditions  for  Evaporation. 
—  Pour  the  same  quantity  of  water  (half  a  glassful)  into 
three  saucers  and  two  bottles.  Place  one  saucer  near  a 
hot  stove ;  place  the  other  two  in  a  cool  place,  having  first 
covered  one  of  them  with  a  dish.  Place  one  of  the  bottles 
by  the  stove  and  the  other  by  the  remaining  saucers.    After 


PRELIMINARY  EXPERIMENTS  xiii 

some  hours,  examine  the  saucers  and  bottles  and  compare 
and  record  the  results.     Explain.     State  three  conditions, 
that  are  favorable  to  evaporation.      State   three   ways  in 
which  evaporation  may  be  prevented  or  decreased. 

Tests  for  Acid,  Alkaline,  and  Neutral  Substances.  —  For 
acid  tests,  use  sour  buttermilk  (which  contains  lactic  acid), 
or  hydrochloric  acid  diluted  in  ten  parts  water,  or  strong 
vinegar  (which  contains  acetic  acid).  Has  the  acid  a  char- 
acteristic ("sour")  odor  and  taste  (test  it  only  when  very 
dilute)?  Rub  dilute  acid  between  the  fingers;  how  does 
it  feel  ?  Is  there  any  effect  on  the  fingers  ?  Obtain  litmus 
paper  at  a  druggist's.  Dip  a  strip  of  red  litmus  and  of 
blue  litmus  paper  into  the  acid.     What  result  ? 

For  alkaline  tests,  dissolve  in  a  glass  of  water  a  spoonful 
of  baking  soda  or  some  laundry  soap  ;  or  dissolve  an  inch 
stick  of  caustic  soda  in  a  glass  of  water.  Test  odor  and 
"  feel  "  of  last  solution  as  with  the  acid  ;  likewise  test  effect 
of  alkaline  solution  on  red  and  blue  litmus  paper.  Record 
results.  Alkalies  are  strong  examples  of  a  more  general 
class  of  substances  called  bases,  which  have  the  opposite 
effect  from  acids. 

Test  pure  water.  Has  it  odor  ?  A  taste  ?  Test  it  with 
red  and  blue  litmus  paper.  Water  is  a  neutral  substance : 
that  is,  it  is  neither  an  acid  nor  an  alkali  (or  base). 

After  making  appropriate  tests,  write  ac,  al,  or  neu  after 
each  name  in  the  following  list  (or  write  in  three  columns) ; 
vinegar,  soda,  saliva,  sugar,  juice  of  apple,  lemon,  and 
other  fruits,  milk,  baking  powder,  buttermilk,  ammonia, 
salt  water. 

Pour  some  of  the  alkaline  solution  into  a  dish,  gradually 
add  dilute  acid  (or  sour  buttermilk),  stirring  with  glass  rod 
and  testing  with  litmus  until  the  mixture  does  not  turn  red 
litmus  blue  nor  blue  litmus  red.     The  acid  and  alkali  are 


xiv  GENERAL    INTRODUCTION 

then  said  to  have  neutralized  each  other,  and  the  resulting 
substance  is  called  a  salt.  The  salt  may  be  obtained  by 
evaporating  the  water  of  the  solution.  Most  common 
minerals  are  salts.  If  the  last  experiment  is  tried  with 
soda  and  sour  buttermilk,  the  demonstration  will  show 
some  of  the  facts  involved  in  bread  making  with  the  use 
of  these  substances. 

Test  for  Starch.  —  Starch  turns  blue  with  iodine.  The 
color  may  be  driven  away  by  heat,  but  will  return  again  as 
the  temperature  lowers.  Procure  a  few  cents'  worth  of  tinc- 
ture of  iodine  and  dilute  it.  Get  a  half  dozen  pieces  of 
paper  and  cardboard,  all  different,  and  test  each  for  starch 
by  placing  it  over  mouth  of  bottle  and  tipping  the  bottle 
up.  If  much  starch  is  present  the  spot  will  be  blue-black 
or  dark  blue  ;  if  little  starch,  pale  blue  ;  if  no  starch,  brown 
or  yellowish. 

Make  pastes  with  wheat  flour,  potato  starch,  and  corn 
starch.  Treat  a  little  of  each  with  a  solution  of  rather 
dilute  tincture  of  iodine.  Try  grains  from  crushed  rice 
with  the  same  solution.  Are  they  the  same  color  ?  Cut 
a  thin  section  from  a  potato,  treat  with  iodine  and  examine 
under  the  microscope. 

To  study  Starch  Grains.  —  Mount  in  cold  water  a  few 
grains  of  starch  from  each  of  the  following  :  potato,  wheat, 
arrowroot  (buy  at  drug  store),  rice,  oats,  corn.  Study  under 
microscope  the  sizes,  forms,  layers,  fissures,  and  location 
of  nuclei,  and  make  a  drawing  of  a  few  grains  of  each. 

Test  for  Grape  Sugar.  —  Make  a  thick  section  of  a  bit  of 
the  edible  part  of  a  pear  and  place  it  in  a  bath  of  Fehling's 
solution.  After  a  few  moments  boil  the  liquid  containing 
the  section  for  one  or  two  minutes.  It  will  turn  to  an 
orange  color,  showing  a  deposit  of  an  oxid  of  copper  and 
perhaps  a  little  copper  in  the  metallic  form.     A  thin  sec- 


PRELIMINARY  EXPERIMENTS  XV 

tion  treated  in  like  manner  may  be  examined  under  the 
microscope,  and  the  fine  particles,  precipitated  from  the 
sugar  of  the  pear,  may  be  clearly  seen.  {Fehlings  solution 
is  made  by  taking  one  part  each  of  these  three  solutions 
and  two  parts  of  water:  (i)  Copper  sulfate,  9  grams  in 
250  cubic  centimeters  of  water;  (2)  sodium  hydroxid,  30 
grams  in  250  c.c.  water;  (3)  Rochelle  salts,  43  grams  in 
250  c.c.  water.) 

Test  for  Nitrogenous  Substances,  or  Proteids.  —  Put  a  little 
white  of  egg  into  a  test  tube  and  heat  slowly.  What  change 
takes  place  in  the  egg  ?  Put  another  part  of  the  white  of 
egg  into  a  test  tube  and  add  dilute  nitric  acid.  Compare 
the  results  of  the  two  experiments.  White  of  egg  is  an  ex- 
ample of  a  proteid  ;  that  is,  it  is  the  form  of  nitrogen  most 
commonly  found  in  plant  and  animal  tissue,  and  it  can  be 
formed  only  by  life  processes.  Do  acid  and  heat  harden 
or  soften  most  substances  ?  Either  of  the  above  tests 
reveal  proteid,  if  present.  Does  cooking  tend  to  soften  or 
toughen  lean  meat  ? 

Another  test  for  proteid  is  nitric  acid,  which  turns  pro- 
teid (and  hardly  anything  else)  yellow.  Proteid  when 
burned  has  a  characteristic  odor  ;  this  will  be  noticed  if  lean 
meat  or  cheese  is  charred  in  a  spoon.  The  offensive  odor 
from  decomposing  proteid  is  also  characteristic,  whether 
it  comes  from  stale  beans,  meat,  mushrooms,  or  other 
things  containing  proteid. 

Test  for  Fats  and  Oils.  —  Place  a  little  tallow  from  a 
candle  on  unglazed  paper  and  warm.  Hold  the  paper  up 
to  the  light  and  examine  it.  What  effect  has  the  fat  had  on 
the  paper  ?  Place  a  little  starch,  sugar,  powdered  chalk,  or 
white  of  egg  on  paper  and  repeat  the  experiment ;  is  the 
effect  the  same  ?  Place  some  of  the  tallow  in  a  spoon,  and 
heat.     Compare   the   effect  of    heat  on   fat  and    proteid. 


XVI  GENERAL   INTRODUCTION 

Water  also  makes  paper  semi-transparent,  but  it  soon 
evaporates  :  fat  does  not  evaporate. 

Another  test  for  fats  is  to  mount  a  thin  section  of  the 
endosperm  of  castor-oil  seed  in  water  and  examine  with 
high  power.  Small  drops  of  oil  will  be  quite  abundant. 
Treat  the  mount  with  alcanin  (henna  root  in  alcohol). 
The  drops  of  oil  will  stain  red.  This  is  a  standard  test  for 
fats  and  oils. 

To  make  or  liberate  Oxygen.  —  If  there  is  a  chemistry 
class  in  school,  one  of  its  members  will  doubtless  be  glad 
to  prepare  some  of  the  gas  called  oxygen,  and  furnish 
several  glass  jars  filled  with  it  to  the  biology  class.  If  it 
is  desired  to  make  oxygen,  the  following  method  may 
be  employed :  Provide  a  dry  glass  flask  of  three  to 
four  ounces  capacity.  It  shouM  have  a  glass  delivery 
tube,  inserted  through  a  one-holed  rubber  stopper,  and 
so  bent  as  to  pass  under  the  surface  of  water  contained 
in  a  deep  dish.  Fill  several  pint  fruit-jars  with  water, 
cover  with  pieces  of  stiff  pasteboard,  and  turn  mouth 
downwards  in  the  dish  of  water.  From  one  half  to 
two  thirds  ounces  of  an  equal  mixture  of  potassium 
chlorate  and  manganese  dioxid  (procured  at  drug  store) 
is  put  in  the  flask  and  heated  by  means  of  a  gas  or 
alcohol  lamp.  When  the  oxygen  begins  to  form,  collect 
some  in  jars  by  inserting  the  end  of  delivery  tube  under 
the  jars  as  they  stand  in  water.  Caution:  Remove 
delivery  tube  from  water  before  cooling  the  flask,  to  pre- 
vent any  water  being  drawn  back. 

Oxidation.  —  That  something  besides  wood  or  coal  is 
necessary  to  a  fire  can  be  shown  by  shutting  off  entirely 
the  draught  of  a  stove.  Fire  and  other  forms  of  combus- 
tion depend  on  a  process  called  oxidation.  This  consists 
in  the  uniting  of  oxygen  with   other  substances.      When 


PRELIMINARY  EXPERIMENTS  XV11 

wood  decays,  the  carbon  in  it  oxidizes  (unites  with  oxygen)        L-= 

and  carbon  dioxid  gas  is  formed.     When  wood  burns,  the> 

oxidation  is  more  rapid.  When  iron  oxidizes,  iron  rust  is 
formed.  When  hydrogen  is  oxidized,  water  is  formed,  i 
Kerosene  oil  contains  hydrogen,  and  water  is  formed  when 
it  is  burned.  Almost  every  one  has  noticed  the  cloud  of 
moisture  which  collects  on  the  chimney  when  the  lamp  is 
first  lighted.  By  using  a  chimney  which  has  been  kept 
in  a  cold  place,  the  moisture  becomes  apparent ;  soon 
the  chimney  becomes  hot  and  the  water  no  longer  collects, 
but  it  continues  to  pass  into  the  room  as  long  as  the  lamp 
burns.  Fats  also  contain  hydrogen.  Hold  a  piece  of  cold 
glass  or  an  inverted  tumbler  above  the  flame  of  a  tallow 
candle.     Does  water  collect  on  it  ? 

Oxidation  may  be  said  to  be  the  basis  of  all  life  processes  / 
for  this  reason  :  oxidation  gives  rise  to  heat  and  sets  free 
energy,  and  all  living  things  need  heat  and  energy  in  order 
to  grow  and  live.  The  heat  of  animals  is  very  noticeable. 
The  oxidation  in  plants  also  forms  a  slight  amount  of  heat. 
In  both  animals  and  plants  oxidation  is  much  slower  than 
in  ordinary  fires.  That  heat  is  formed  even  in  slow  oxida- . 
tion  is  shown  by  fires  which  arise  spontaneously  in  masses 
of  decaying  material.  The  rotting  of  wood  is  not  only 
accompanied  by  heat  but  sometimes  by  light,  as  when 
"  fox  fire  "  is  emitted.  Rub  the  end  of  a  match  on  your 
finger  in  the  dark.  Explain  the  result.  Strike  a  match 
and  notice  the  white  fumes  which  rise  for  an  instant. 
These  fumes  are  not  ordinary  smoke  (particles  of  carbon), 
but  they  are  oxid  of  phosphorus.  Why  will-  water  (oxid 
of  hydrogen)  not  burn  ?  Sand  is  oxid  of  silicon.  Explain 
how  throwing  sand  on  a  fire  puts  it  out.  [See  also  experi- 
ments with  candle  and  breath,  in  Introduction  to  Human 
Biology.] 


xviil  GENERAL    INTRODUCTION 

Inorganic  and  Organic  Matter.  —  Test  for  Minerals.  — 
The  earth  was  once  in  a  molten  condition,  which  would 
have  destroyed  any  combustible  material  if  any  had  then 
existed.  'Before  plants  and  animals  existed,  the  earth  con- 
sisted mostly  of  incombustible  minerals,  known  as  inorganic 
matter.  Substances  formed  by  animals  and  plants  are 
organic  tnattcr,  so  called  because  built  up  by  organized  or 
organ-bearing  or  living  things  ;  starch  is  an  example,  being 
formed  in  plants.  Organic  substances  are  composed  chiefly 
of  carbon,  oxygen,  hydrogen,  and  nitrogen.  (See  page  I 
of  "Animal  Biology.")  Coal-oil,  and  all  combustible  ma- 
terials have  their  origin  in  life.  Hence,  burning  to  find 
whether  there  is  an  incombustible  residue  is  also  a  test  for 
minerals.  Meat,  bread,  oatmeal,  bone,  wood,  may  be  tested 
for  mineral  matter  by  burning  in  a  spoon  held  over  a  hot 
fire,  or  flame  of  gas  or  lamp.  The  substance  being  tested 
should  be  burned  until  all  black  material  (which  is  organic 
carbon  and  not  a  mineral)  has  disappeared.  Any  residue 
will  be  mineral  matter. 

Protoplasm.  —  Inside  the  cells  of  plants  and  animals  is 
the  living  substance,  known  as  protoplasm.  It  is  a  struc- 
tureless, nearly  or  quite  colorless,  transparent  jelly-like 
substance  of  very  complex  and  unstable  composition. 
Eighty  per  cent  or  more  is  water  ;  the  remainder  is  pro- 
teid,  fats,  oils,  sugars,  and  salts.  Protoplasm  has  the 
power  of  growth  and  reproduction  ;  it  can  make  living  sub- 
stance from  dead  or  lifeless  substances.  It  has  the  power 
of  movement  within  the  cell,  and  it  is  influenced  (or  is  irrita- 
ble) by  heat,  light,  touch,  and  other  stimuli.  When  proto- 
plasm dies  the  organism  dies. 

Physics  is  the  science  that  treats  of  the  properties  and 
phenomena  (or  behavior)  of  matter  or  of  objects ;  as  of 
such  properties  or  phenomena  or  agencies  as  heat,  light, 


\ 


PRELIMINARY  EXPERIMENTS  XIX 

force,  electricity,  sound,  friction,  density,  weight,  and  the 
like. 

Chemistry  is  the  science  that  treats  of  the  composition  of 
matter.  All  matter  is  made  up,  as  we  have  seen,  of  ele- 
ments. Very  few  elements  exist  in  nature  in  a  free  or 
uncombined  form.  The  nitrogen  and  oxygen  of  the  air 
are  the  leading  uncombined  elements. 

In  order  to  express  the  chemical  combinations  clearly, 
symbols  are  used  to  represent  each  element,  and  these 
symbols  are  then  combined  to  represent  the  proportions 
of  each  in  the  compound.  If  C  stands  for  carbon  and  O 
for  oxygen,  the  carbon  dioxid  might  be  represented  by  the 
formula  COO.  In  order  to  avoid  the  repetition  of  any 
letter,  however,  a  number  is  used  to  denote  how  many 
times  the  element  is  taken  :  thus  the  formula  always  used 
for  carbon  dioxid  is  C02.  The  formula  for  hydrogen 
oxid,  or  water,  is  H20  ;  that  for  starch  is  C6H10O5.  N 
stands  for  nitrogen ;  P,  for  phosphorus ;  K,  potassium ; 
Fe,  iron  ;  S,  sulfur. 

Biology  is  the  science  that  treats  of  life;  that  is,  of  all 
knowledge  of  plants  and  animals  of  all  kinds.  (See  page 
i,  "Animal  Biology.") 

How  a  Candle  Burns 

Some  of  the  foregoing  suggestions  may  be  readily  explained 
and  illustrated  by  simple  experiments  with  a  burning  candle. 
The  following  directions  for  such  experiments  are  by  G.  W. 
Cavanaugh. 

The  materials  needed  for  this  exercise  are  :  a  piece  of  candle 
about  two  inches  long,  a  lamp  chimney  (one  with  a  plain  top  is 
best),  a  piece  of  white  crockery  or  window  glass,  a  piece  of  fine 
wire  about  six  inches  long,  a  bit  of  quicklime  about  half  the 
size  of  an  egg,  and  some  matches.  All  of  these,  with  the  possible 
exception  of  the  quicklime,  can  be  obtained  in  any  household. 


XX 


GENERAL   INTRODUCTION 


If  you  perform  the  experiment  requiring  the  lime,  be  sure  that  you 
start  with  a  fresh  piece  of  quick  or  stone  lime,  which  can  be  had 
of  any  lime  or  cement  dealer.  During  the  performance  of  the 
following  simple  experiments,  the  pupil  should  describe  what  he 
sees  at  each  step.  The  questions  inserted  in  the  text  are  offered 
merely  as  suggestions  in  the  development  of  the  desired  ideas. 
The  answers  are  those  which  it  is  desired  the  pupils  shall  reach 
or  confirm  by  their  own  observation. 


I .    Oxygen 

Light  the  candle  and  place  it  on  a  piece  of  blotting 
paper  (A).     What  do  you  see  burning  ?     Is  anything  burn- 
ing besides  the  candle  ?     The  answer 
will  probably  be  "  no."     Let  us  see. 

Place  the  lamp  chimney  over  the 
lighted  candle,  and  partly  cover  the 
top  by  a  piece  of  stiff  paper,  as  in 
Fig.  A.  Ask  the  pupils  to  observe 
and  describe  how  the  flame  goes  out ; 
i.e.  that  it  is  gradually  extinguished 
and  does  not  go  out  instantly.  Why 
did  the  flame  go  out  ?  The  probable 
thought  will   be, 


A.  —  The  Beginning  of 
the  Candle  Ex- 
periment. 


"  Because  there  was  no  air."  (If  there 
was  no  air  within  the  chimney,  some 
could  have  entered  at  the  top.) 

Place  two  pencils  beside  the  re- 
lighted candle  and  on  them  the  chim- 
ney (B).  What  is  the  difference  be- 
tween the  way  in  which  the  candle 
burns  now  and  before  the  chimney 
was  placed  over  it?  It  flickers,  or 
dances    about    more.      What    makes 


B.  —  Supplying  Air  un- 
derneath the  Chim- 
ney. 


PRELIMINARY  EXPERIMENTS  XXI 

boys  and  girls  feel  like  dancing  about  when  they  go  out 
from  a  warm  schoolroom  ?  What  makes  the  flame  dance 
or  flicker  when  the  chimney  is  raised  by  the  pencils  ? 
Because  it  gets  fresh  air  under  the  chimney. 

Repeat  the  first  experiment,  in  which  the  flame  grows 
gradually  smaller  till  it  is  extinguished.  Why  does  the 
flame  die  out  now  ?  Is  it  really  necessary  to  have  fresh 
air  in  order  to  keep  a  flame  burning? 

To  prove  this  further,  let  the  candle  be  relighted.  Place 
the  chimney  over  it,  now  having  the  top  completely  closed 
by  a  piece  of  paper.  Have  ready  a  lighted  splinter  or 
match,  and  just  as  soon  as  the  candle  is  extinguished 
remove  the  paper  from  the  chimney  top  and  thrust  in  the 
lighted  splinter.  Why  does  the  light  on  the  splinter  go 
out  ?  What  became  of  the  freshness  that  was  in  the  air  ? 
It  was  destroyed  by  the  burning  candle. 

Evidently  there  is  some  decided  difference  between  un- 
burned  air  and  burned  air,  since  a  flame  can  continue  to 
burn  only  in  air  that  has  the  quality  known  as  freshness. 
This  quality  of  fresh  air  is  due  to  oxygen,  represented  by  O. 
Why  was  the  splinter  put  out  instantly,  while  the  candle 
flame  died  out  gradually  ?  When  the  splinter  was  thrust 
in,  the  air  had  no  freshness  or  oxygen  at  all,  while  when 
the  candle  was  placed  under  the  chimney,  it  had  whatever 
oxygen  was  originally  in  the  air  within  the  chimney. 

Endeavor  to  have  this  point  clearly  understood  :  that  the 
candle  did  not  go  out  as  long  as  the  air  had  any  oxygen 
and  that  the  splinter  was  extinguished  immediately  because 
there  was  no  oxygen  left. 

Relight  the  candle.  A  former  question  may  now  be 
repeated  :    Is  anything  else  burning  besides  the  candle  ? 

When  the  subject  of  the  necessity  of  fresh  air  and  con- 
sequently of  oxygen  for  the  burning  of  the  candle  seems 


C EA  ERA L   IN TR  ODl'C  TION 


to  be  understood,  the  following  questions,  together  with 
any  others  which  suggest  themselves,  may  be  asked:  What 
is  the  reason  that  draughts  are  opened  in  stoves  ?  Why  is 
the  bottom  of  a  "burner"  on  a  lamp  always  full  of  holes? 


II.    Carbon 

Let  us  now  observe  the  blackened  end  of  a  burned  match 
or  splinter.  This  black  substance  is  usually  known  by  the 
name  of  charcoal.  If  handled,  it  will  blacken  the  fingers. 
Try  this.  The  same  substance  is  found  on  the  bottoms  of 
kettles  which  have  been  used  over  a  wood  fire,  but  it  is 
there  a  fine  powder. 

Let  us  see  what  was  burning  when  the  candle  was 
lighted,  besides  the  oxygen  in  the  air.  Relight  the  candle 
and  hold  the  porcelain  or  glass  about 
an  inch  above  the  bright  part  of  the 
flame.  What  happens  to  it  there  ? 
Next,  lower  it  directly  into  the  flame 
(C).  What  is  the  black  stuff  that 
gets  on  the  glass  ?  Look  closely  and 
see  whether  it  is  not  deposited  here 
also  as  a  fine  powder.  Will  this  de- 
posit from  the  candle  blacken  the 
fingers  ? 

Instead  of  using  the  name  charcoal  for  this  black  sub- 
stance, let  us  call  it  carbon,  the  better  name,  because 
there  are  several  kinds  of  carbon,  and  charcoal  is  only 
that  kind  which  is  rather  light  and  easily  blackens  the 
hands. 

The  carbon  from  the  candle  flame  came  mostly  from  the 
wax  or  tallow  ;  only  a  very  small  part  came  from  the  wick. 
It  cannot  be  seen  in  the  tallow,  neither  can  it  be  seen  in 


C  —  The  Carbon  (or 
Soot)  is  deposited 
on  the  Glass. 


PRELIMINARY  EXPERIMENTS  xxiii 

unburned  wood,  and  yet  it  can  be  found  when  the  wood  is 
partly  burned. 

Why,  now,  is  the  glass  blackened  when  held  in  the  flame 
and  not  when  held  directly  above  it?  It  is  because  the 
carbon  from  the  candle  has  not  been  completely  burned 
at  the  middle  of  the  flame  ;  but  it  is  burned  beyond  the 
bright  part  of  the  flame.  When  the  glass  is  held  in  the 
flame,  the  carbon  that  is  not  yet  completely  burned  is  de- 
posited on  it,  because  it  is  cooler  than  that  in  the  surround- 
ing flame. 

A  fine  deposit  of  carbon  can  be  had  from  any  of  the 
luminous  parts  of  the  flame;  and  it  is  these  thousands  of 
little  particles  of  carbon,  getting  white  hot,  which  glow 
like  coals  in  the  stove  and  make  the  light.  Just  as  soon 
as  they  are  completely  burned,  there  is  no  more  light,  as 
coals  cease  to  glow  when  burned  to  ashes. 


III.    Carbon  dioxid 

Let  us  now  inquire  what  becomes  of  the  carbon  that  we 
find  in  the  bright  part  of  the  flame  and  of  the  oxygen  that 
was  in  the  air  in  the  lamp  chimney.  When  the  candle  was 
extinguished  within  the  chimney,  there  was  no  oxygen  left, 
as  shown  by  the  lighted  splinter,  which  was  put  out  immedi- 
ately. Neither  could  any  of  the  particles  of  carbon  be 
found  except  on  the  wick.  Yet  they  both  still  exist  within 
the  chimney,  but  in  an  entirely  different  condition.  While 
the  candle  was  burning,  the  little  particles  of  carbon  that 
we  find  ascending  in  the  flame  are  joining  with  the  oxygen 
of  the  air  and  making  an  entirely  new  substance.  This 
new  substance  is  a  gas  and  cannot  be  seen  in  the  air. 

Of  what  two  substances  is  this  new  substance  made  ? 
It  is  COo- 


A  — The  Test 
wmii  i  in.  Si  s- 
pbnded     Film 

OF  LlMKWATER. 


xxjv  //    INTRODUCTION 

Place  .1  bit  of  quicklime  in  about  half  a  glass  of  water 
on  the  day  previous  to  the  experiment.  When  ready  for 
use  there  will  be  a  white  sediment  at  the  bottom  and  a  thin 
white  scum  en  the  top  of  the  clear  lime- 
water.  The  pupils  should  see  this  white 
scum,  as  a  question  about  it  will  follow. 
Make  a  loop  in  the  end  of  the  piece  of 
wire  by    turning  it   around  the   point   oi    a 

lead  pencil.  Remove  the  scum  from  the 
limewater  with  a  piece  of  paper  and  insert 
the  loop  into  the  clear  water.  When 
withdrawn,  the  loop  ought  to  hold  a  film 
of  clear  water.  Pass  the  wire  through  a 
piece  of  cardboard  or  stiff  paper,  and 
arrange  as  shown  in  D. 
Place  the  chimney  over  the  lighted  candle.  Lower  the 
loop  into  the  chimney  and  cover  the  top  of  the  chimney 
with  the  paper.  Withdraw  the  wire  two  minutes  after  the 
candle  goes  out.  Note  the  cloudy  appearance  of  the  film 
of  water  on  the  wire.  The  cloudiness  was  caused  by  the 
carbon  dioxid  formed  while  the  candle  was  burning. 

Omitting  the  candle,  hang  the  freshly  wetted  wire  in  the 
empty  chimney.  Let  the  film  of  limewater  remain  within 
the  chimney  for  the  same  length  of  time  as  when  the  can- 
dle was  used.  It  does  not  become  cloudy  now.  The 
cloudiness  in  clear  limewater  is  a  test  or  indication  that 
carbon  dioxid  is  present. 

What  caused  the  white  scum  on  the  limewater  which 
stood  overnight  ? 

How  does  the  C02  get  into  the  air  ?  It  is  formed  when- 
ever wood,  coal,  oil,  or  gas  is  burned. 

The  amount  of  CO.,  in  ordinary  air  is  very  small,  being 
only  three  parts  in  ten  thousand.     If  the  limewater  in  the 


PRELIMINARY  EXPERIMENTS  XXV 

loop  be  left  long  enough  in  the  air,  it  will  become  cloudy. 
The  reason  it  clouds  so  quickly  when  the  candle  is  being 
burned  is  that  a  large  amount  of  C02  is  formed.  Besides 
being  made  by  real  flames,  C02  is  formed  every  time  we 
breathe  out  air.  Renew  the  film  of  water  in  the  loop  and 
breathe  against  it  gently  for  two  or  three  minutes. 

The  presence  of  C02  in  the  breath  may  be  shown  better 
by  pouring  off  some  of  the  clear  limewater  into  a  clean 
glass  and  blowing  into  it  through  a  straw. 

Why  does  water  put  out  a  fire  ?  The  answer  is,  not 
alone  because  it  wets  and  shuts  off  the  supply  of  free 
oxygen,  but  because  it  cools  the  carbon,  which  must  be 
hot  in  order  to  unite  with  the  oxygen,  and  prevents  the 
oxygen  of  the  air  from  getting  as  near  the  carbon  as 
before. 


PLANT   BIOLOGY 

CHAPTER    I 

NO   TWO    PLANTS   OR   PARTS   ARE   ALIKE 


Fig.  i.  —  No  Two  Branches  are  Alike. 
(Hemlock.) 

If  one  compares  any  two  plants  of 
the  same  kind  ever  so  closely,  it  will  be 
found  that  they  differ  from  each  other.  The 
difference  is  apparent  in  size,  form,  color,  mode 
of  branching,  number  of  leaves,  number  of  flowers,  vigor, 
season  of  maturity,  and  the  like  ;  or,  in  other  words,  all 
plants  and  animals  vary  from  an  assumed  or  standard  type. 
If  one  compares  any  tivo  branches  or  tivigs  on  a  tree,  it 
will  be  found  that  they  differ  in  size,  age,  form,  vigor,  and 
in  other  ways  (Fig.  i). 

If  one  compares  any  two  leaves,  it  will  be  found  that 
they  are  unlike  in  size,  shape,  color,  veining,  hairiness, 
markings,  cut  of  the  margins,  or  other  small  features.  In 
some  cases  (as  in  Fig.  2)  the  differences  are  so  great  as  to 
be  readily  seen  in  a  small  black-and-white  drawing. 
B  1 


PLANT  BIOLOGY 


If  the  pupil  extends  his  observation  to  animals,  he 
will  still  find  the  same  truth;  for  probably  no  two  living 
objects  arc  exact  duplicates.  If  any  person  finds  two  objects 
that  he  thinks  to  be  exactly  alike,  let  him  set  to  work  to 


Fig.  2.  — No  Two  Leaves  are  Alike. 

discover   the    differences,    remembering    that    notliing    in 
nature  is  so  small  or  apparently  trivial  as  to  be  overlooked. 

Variation,  or  differences  between  organs  and  also  be- 
tween organisms,  is  one  of  the  most  significant  facts  in 
nature. 

Suggestions. — The  first  fact  that  the  pupil  should  acquire 
about  plants  is  that  no  two  are  alike.  The  way  to  apprehend  this 
great  fact  is  to  see  a  plant  accurately  and  then  to  compare  it  with 


NO    TWO  PLANTS   OR  PARTS  ARE  ALIKE  3 

another  plant  of  the  same  species  or  kind.  In  order  to  direct  and 
concentrate  the  observation,  it  is  well  to  set  a  certain  number  of 
attributes  or  marks  or  qualities  to  be  looked  for.  1.  Suppose 
any  two  or  more  plants  of  corn  are  compared  in  the  following 
points,  the  pupil  endeavoring  to  determine  whether  the  parts 
exactly  agree.  See  that  the  observation  is  close  and  accurate. 
Allow  no  guesswork.  Instruct  the  pupil  to  measure  the  parts 
when  size  is  involved  : 

(1)  Height  of  the  plant. 

(2)  Does  it  branch?    How  many  secondary  stems  or  "suck- 
ers" from  one  root? 

(3)  Shade  or  color. 

(4)  How  many  leaves? 

(5)  Arrangement  of  leaves  on  stem. 

(6)  Measure  length  and  breadth  of  six  main  leaves. 

(7)  Number  and  position  of  ears  ;  color  of  silks. 

(8)  Size  of  tassel,  and  number  and  size  of  its  branches. 

(9)  Stage  of  maturity  or  ripeness  of  plant. 

(10)  Has  the  plant  grown  symmetrically,  or  has  it  been 
crowded  by  other  plants  or  been  obliged  to  struggle  for  light 
or  room  ? 

(ti)    Note  all  unusual  or  interesting  marks  or  features. 

(12)    Always  make  note  of  comparative  vigor  of  the  plants. 

Note  to  Teacher.  —  The  teacher  should  always  insist  on  per- 
sonal work  by  the  pupil.  Every  pupil  should  handle  and  stitay 
the  object  by  himself.  Books  and  pictures  are  merely  guides  and 
helps.  So  far  as  possible,  study  the  plant  or  animal  just  where  it 
grows  naturally. 

Notebooks. — Insist  that  the  pupils  make  full  notes  and  preserve 
these  notes  in  suitable  books.  Note-taking  is  a  powerful  aid  in 
organizing  the  mental  processes,  and  in  insuring  accuracy  of  obser- 
vation and  record.  The  pupil  should  draw  what  he  sees,  even 
though  he  is  not  expert  with  the  pencil.  The  drawing  should  not 
be  made  for  looks,  but  to  aid  the  pupil  in  his  orderly  study  of  the 
object;  it  should  be  a  means  of  self-expression. 

Laboratory.  —  Every  school,  however  small,  should  have  a 
laboratory  or  work-room.  This  work-room  may  be  nothing  more 
than  a  table  at  one  side  of  the  room  where  the  light  is  good. 
Here  the  specimens  may  be  ranged  and  studied.  Often  an 
aquarium  and  terrarium  may  be  added.  A  cabinet  or  set  of 
shelves  should  be  provided  for  a  museum  and  collection. 

The  laboratory  may  be  in  part  out  of  doors,  as  a  school  garden  ; 
or  the  garden  may  be  at  the  pupil's  home,  and  yet  be  under  the 
general  direction  of  the  teacher. 


CHAPTER    II 

THE   STRUGGLE   TO   LIVE 

Every  plant  and  animal  is  exposed  to  unfavorable  eon- 
di/ ions.  It  is  obliged  to  contend  with  these  conditions  in 
order  to  live. 

No  two  plants  or  parts  of  plants  are  identically  exposed 
to  the  conditions  in  which  they  live.     The  large  branches 


^m 


Fig.  3.  — A  Battle  for  Life. 

in  Fig.  1  probably  had  more  room  and  a  better  exposure 
to  light  than  the  smaller  ones.  Probably  no  two  of  the 
leaves  in  Fig.  2  are  equally  exposed  to  light,  or  enjoy 
identical  advantages  in  relation  to  the  food  that  they  re- 
ceive from  the  tree. 

Examine  any  tree  to  determine  under  what  advantages 
or  disadvantages  any  of  the  limbs  may  live.  Examine 
similarly  the  different  plants  in  a  garden  row  (Fig.  3);  or 
the  different  bushes  in  a  thicket ;  or  the  different  trees  in 
a  wood. 

4 


THE   STRUGGLE    TO  LIVE 


5 


The  plant  meets  its  conditions  by  succumbing  to  them 
(that  is,  by  dying),  or  by  adapting  itself  to  than. 

The  tree  meets  the  cold  by  ceasing  its  active  growth, 
hardening  its  tissues,  dropping  its  leaves.  Many  her- 
baceous or  soft-stemmed  plants  meet  the  cold  by  dying 
to  the  ground  and  withdrawing  all  life  into  the  root  parts. 
Some  plants  meet  the  cold  by  dying  outright  and  provid- 
ing abundance  of  seeds  to  perpetuate  the  kind  next  season. 


Fig.  4.  — The  Reach  for  Light  of  a  Tree  on  the  Edge  of  a  Wood. 

Plants  adapt  themselves  to  light  by  growing  toward  it 
(Fig.  4);  or  by  hanging  their  leaves  in  such  position  that 
they  catch  the  light ;  or,  in  less  sunny  places,  by  expand- 
ing their  leaf  surface,  or  by  greatly  lengthening  their 
stems  so  as  to  overtop  their  fellows,  as  do  trees  and  vines." 

The  adaptations  of  plants  will  afford  a  fertile  field  of 
study  as  we  proceed. 


6  PLANT  BIOLOGY 

Struggle  for  existence  and  adaptation  to  conditions  are 
among  the  most  significant  facts  in  nature. 

The  sum  of  all  the  conditions  in  which  a  plant  or  an  ani- 
mal is  placed  is  called  its  environment,  that  is,  its  surround- 
ings. The  environment  comprises  the  conditions  of  climate, 
soil,  moisture,  exposure  to  light,  relation  to  food  supply, 
contention  with  other  plants  or  animals.  TJic  organism 
adapts  itself  to  its  environment,  or  else  it  weakens  or  dies. , 
Every  weak  branch  or  plant  has  undergone  some  hardship 
that  it  was  not  wholly  able  to  withstand. 

Suggestions. — The  pupil  should  study  any  plant,  or  branch  of 
a  plant,  with  reference  to  the  position  or  condition  under  which  it 
grows,  and  compare  one  plant  or  branch  with  another.  With 
animals,  it  is  common  knowledge  that  every  animal  is  alert  to 
avoid  or  to  escape  danger,  or  to  protect  itself.  2.  It  is  well  to 
begin  with  a  branch  of  a  tree,  as  in  Fig.  i.  Note  that  no  two 
parts  are  alike  (Chap.  I).  Note  that  some  are  large  and  strong 
and  that  these  stand  farthest  towards  light  and  room.  Some  are 
very  small  and  weak,  barely  able  to  live  under  the  competition. 
Some  have  died.  The  pupil  can  easily  determine  which  ones  of 
the  dead  branches  perished  first.  He  should  take  note  of  the 
position  or  place  of  the  branch  on  the  tree,  and  determine  whether 
the  greater  part  of  the  dead  twigs  are  toward  the  center  of  the 
tree  top  or  toward  the  outside  of  it.  Determine  whether  acci- 
dent has  overtaken  any  of  the  parts.  3.  Let  the  pupil  examine 
the  top  of  any  thick  old  apple  tree,  to  see  whether  there  is  any 
struggle  for  existence  and  whether  any  limbs  have  perished.  4.  If 
the  pupil  has  access  to  a  forest,  let  him  determine  why  there  are 
no  branches  on  the  trunks  of  the  old  trees.  Examine  a  tree  of 
the  same  kind  growing  in  an  open  field.  5.  A  row  of  lettuce  i 
or  other  plants  sown  thick  will  soon  show  the  competition  between  \ 
plants.  Any  fence  row  or  weedy  place  will  also  show  it.  Why  i 
does  the  farmer  destroy  the  weeds  among  the  corn  or  potatoes? 
How  does  the  florist  reduce  competition  to  its  lowest  terms? 
what  is  the  result? 


CHAPTER    III 


THE   SURVIVAL   OF   THE   FIT 

The  plants  that  most  perfectly  meet  their  conditions  are 
able  to  persist.  They  perpetuate  themselves.  Their  off- 
spring are  likely  to  inherit  some  of  the  attributes  that 
enabled  them  successfully  to  meet  the  battle  of  life.  The 
fit  (those  best  adapted  to  their  conditions)  tend  to  survive. 

Adaptation  to  conditions  depends  on  the  fact  of  varia- 
tion; that  is,  if  plants  were  perfectly  rigid  or  invariable 
(all  exactly  alike)  they  could  not  meet  new  conditions. 
Conditions  are  necessarily  new  for  every  organism.  It  ts 
impossible  to  picture  a  perfectly  inflexible  and  stable  succes- 
sion of  plants  or  animals. 

Breeding.  —  Man  is  able  to  modify  plants  and  animals. 
All   our  common   domestic  animals  are  very  unlike  their 
original   ancestors.      So   all   our   common    and    long-culti- 
vated   plants    have    varied 
from  their  ancestors.    Even 
in    some    plants   that    have 
been  in  cultivation  less  than 
a    century    the    change    is 
marked  :  compare  the  com- 
mon    black-cap     raspberry 
with  its  common  wild  ances- 
tor, or  the  cultivated  black- 
berry with  the  wild  form. 

By  .choosing  seeds  from  a  plant  that   pleases  him,  the 
breeder  may  be  able,  under  given  conditions,  to  produce 

7 


Fig.  5.— Desirable  and  Uxdesirabi  e 

Types  ok  Cotton  Plants.    Why? 


PLANT  BIOLOGY 


numbers  of  plants  with  more 
or  less  of  the  desired  quali- 
ties ;  from  the  best  of  these, 
he  may  again  choose  ;  and  so 
on  until  the  race  becomes 
greatly  improved  (Figs.  5,  6, 
7).  This  process  of  continu- 
ously choosing  the  most  suita- 
ble plants  is  known  as  selec- 
tion. A  some- 
what similar 
process  pro- 
ceeds in  wild 
nature,  and  it 
is  then  known 
as  natural  se- 
lection. 


Fig.  6.  — Flax  Breeding. 

A   is  a  plant  grown  for  seed  production; 
B,  for  fiber  production.      Why  ? 


Suggestions. 
■ — 6.  Every  pu- 
pil should  un- 
dertake at  least 
one  simple  ex- 
periment in  se- 
lection of  seed.  He  may  select  kernels  from  the 
best  plant  of  corn  in  the  field,  and  also  from  the 
poorest  plant, —  having  reference  not  so  much  to 
mere  incidental  size  and  vigor  of  the  plants  that 
may  be  due  to  accidental  conditions  in  the  field, 
as  to  the  apparently  constitutional  strength  and 
size,  number  of  ears,  size  of  ears,  perfectness  of 
ears  and  kernels,  habit  of  the  plant  as  to  sucker- 
ing,  and  the  like.  The  seeds  may  be  saved  and 
sown  the  next  year.  Every  crop  can  no  doubt 
be  very  greatly  improved  by  a  careful  process 
of  selection  extending  over  a  series  of  years. 
Crops  are  increased  in  yield  or  efficiency  in  three 
ways  :  better  general  care  ;  enriching  the  land 
in  which  they  grow ;  attention  to  breeding. 


Fig.  7.  —  Breed- 
ing. 

A,  effect  from  breed- 
ing from  smallest 
grains  (after  four 
years),  average 
head;  B,  result 
from  breeding  from 
the  plumpest  and 
heaviest  grains 
(after  four  years), 
average  head. 


CHAPTER    IV 

PLANT   SOCIETIES 

In  the  long  course  of  time  in  which  plants  have  been 
accommodating  themselves  to  the  varying  conditions  in 
which  they  are  obliged  to  grow,  they  have  become  adapted 
to  every  different  environment.  Certain  plants,  therefore, 
may  live  together  or  near  each  other,  all  enjoying  the 
same  general  conditions  and  surroundings.  These  aggre- 
gations of  plants  that  are  adapted  to  similar  general  con-' 
ditions  are  known  as  plant  societies. 

Moisture  and  temperature  are  the  leading  factors  in  ( 
determining  plant  societies.  The  great  geographical 
societies  or  aggregations  of  the  plant  world  may  con- 
veniently be  associated  chiefly  with  the  moisture  supply, 
as :  wet-region  societies,  comprising  aquatic  and  bog 
vegetation  (Fig.  8);  arid-region  societies,  comprising  desert 
and  most  sand-region  vegetation ;  mid-region  societies, 
comprising  the  mixed  vegetation  in  intermediate  regions 
(Fig.  9),  this  being  the  commonest  type.  Much  of  the 
characteristic  scenery  of  any  place  is  due  to  its  plant 
societies.  Arid-region  plants  usually  have  small  and  hard 
leaves,  apparently  preventing  too  rapid  loss  of  water. 
Usually,  also,  they  are  characterized  by  stiff  growth,  hairy 
covering,  spines,  or  a  much-contracted  plant-body,  and 
often  by  large  underground  parts  for  the  storage  of  water. 

Plant  societies  may  also  be  distinguished  with  reference 
to  latitude  and  temperature.  There  are  tropical  societies, 
temperate-region    societies,    boreal   or    cold-region   societies. 

9 


10 


PLANT  BIOLOGY 


With  reference  to  altitude,  societies  might  be  classified 
as  lowland  (which  are  chiefly  wet-region),  intermediate 
(chiefly  mid-region),  subalpine  or  mid-mountain  (which  are 
chiefly  boreal),  alpine  or  high-mountain. 

The  above  classifications  have  reference  chiefly  to  great 
geographical  floras  or  societies.  But  there  are  societies 
within  societies.  There  are  small  societies  coming  within 
the  experience  of  every  person  who  has  ever  seen  plants 


Fig.  8.  —  A  Wet-region  Society. 

growing  in  natural  conditions.  There  are  roadside,  fence- 
row,  lawn,  thicket,  pasture,  dune,  woods,  cliff,  barn-yard 
societies.  Every  different  place  has  its  characteristic  vegeta- 
tion. Note  the  smaller  societies  in  Figs.  8  and  9.  In  the 
former  is  a  water-lily  society  and  a  cat-tail  society.  In 
the  latter  there  are  grass  and  bush  and  woods  societies. 

Some  Details  of  Plant  Societies.  —  Societies  may  be  com- 
posed of  scattered  and  intermingled  plants,  or  of  dense 
clumps  or  groups  of  plants.  Dense  clumps  or  groups  are 
usually  made  up  of  one  kind  of  plant,  and  they  are  then 


PI.AXT  SOCIETIES 


I  I 


called  colonies.  Colonies  of  most  plants  are  transient : 
after  a  short  time  other  plants  gain  a  foothold  amongst 
them,  and  an  intermingled  society  is  the  outcome.  Marked 
exceptions  to  this  are  grass  colonies  and  forest  colonies,  in 
which  one  kind  of  plant  may  hold  its  own  for  years  and 
centuries. 

In  a  large  newly  cleared  area,  plants  usually  first  estab- 
lish themselves  in  dense  colonies.     Note  the  great  patches 


Fig.  9.  — A  Mid-region  Society. 

of  nettles,  jewel-weeds,  smart-weeds,  clot-burs,  fire-weeds 
in  recently  cleared  but  neglected  swales,  also  the  fire-weeds 
in  recently  burned  areas,  the  rank  weeds  in  the  neglected 
garden,  and  the  ragweeds  and  May-weeds  along  the  re- 
cently worked  highway.  The  competition  amongst  them- 
selves and  with  their  neighbors  finally  breaks  up  the 
colonies,  and  a  mixed  and  intermingled  flora  is  generally 
the  result. 

In  many  parts  of  the  world  the  general  tendency  of  neg- 
lected areas  is  to  run  into  forest.     All   plants  rush  for  the 


12 


PLANT  BIOLOGY 


cleared  area.  Here  and  there  bushes  gain  a  foothold. 
Young  trees  come  up  ;  in  time  these  shade  the  bushes  and 
gain  the  mastery.  Sometimes  the  area  grows  to  poplars 
or  birches,  and  people  wonder  why  the  original  forest  trees 
do  not  return  ;  but  these  forest  trees  may  be  growing  unob- 
served here  and  there  in  the  tangle,  and  in  the  slow  pro- 
cesses of  time  the  poplars  perish  —  for  they  are  short-lived 
—  and  the  original  forest  may  be  replaced.  Whether  one 
kind  of  forest  or  another  returns  will  depend  partly  on  the 
kinds  that  are  most  seedful  in  that  vicinity  and  which, 
therefore,  have  sown  themselves  most  profusely.  Much 
depends,  also,  on  the  kind  of  undergrowth  that  first  springs 
up,  for  some  young  trees  can  endure  more  or  less  shade 
than  others. 

Some  plants  associate.  They  grow  together.  This  is 
possible  largely  because  they  diverge  or  differ  in  charac- 
ter. Plants  asso- 
ciate in  two  ways : 
by  growing  side  by 
side ;  by  growing 
above  or  beneath. 
In  sparsely  popu- 
lated societies, 
plants  may  grow 
alongside  each 
other.  In  most 
cases,  however, 
there  is  overgrowth 
and  undergrowth  : 
one  kind  grows  beneath  another.  Plants  that  have  be- 
come adapted  to  shade  are  usually  undergrowth s.  In  a  cat- 
tail swamp,  grasses  and  other  narrow-leaved  plants  grow 
in  the  bottom,  but  they  are  usually  unseen  by  the  casual 


Fig.  io.  —  Overgrowth  and  Undergrowth  in 
Three  Series,  —  trees,  bushes,  grass. 


PLANT  SOCIETIES  1 3 

observer.  Note  the  undergrowth  in  woods  or  under  trees 
(Fig.  10).  Observe  that  in  pine  and  spruce  forests  there 
is  almost  no  undergrowth,  partly  because  there  is  very  little 
light. 

On  the  same  area  the  societies  may  differ  at  different 
times  of  the  year.  There  are  spring,  summer,  and  fall  soci- 
eties. The  knoll  which  is  cool  with  grass  and  strawber- 
ries in  June  may  be  aglow  with  goldenrod  in  September. 
If  the  bank  is  examined  in  May,  look  for  the  young  plants 
that  are  to  cover  it  in  July  and  October ;  if  in  Septem- 
ber, find  the  dead  stalks  of  the  flora  of  May.  What  suc- 
ceeds the  skunk  cabbage,  hepaticas,  trilliums,  phlox,  violets, 
buttercups  of  spring  ?  What  precedes  the  wild  sunflowers, 
ragweed,  asters,  and  goldenrod  of  fall  ? 

The  Landscape.  —  To  a  large  extent  the  color  of  the  land- 
scape is  determined  by  the  character  of  the  plant  societies. 
Evergreen  societies  remain  green,  but  the  shade  of  green 
varies  from  season  to  season ;  it  is  bright  and  soft  in 
spring,  becomes  dull  in  midsummer  and  fall,  and  assumes 
a  dull  yellow-green  or  a  black-green  in  winter.  Deciduous 
societies  vary  remarkably  in  color — from  the  dull  browns 
and  grays  of  winter  to  the  brown  greens  and  olive-greens 
of  spring,  the  staid  greens  of  summer,  and  the  brilliant 
colors  of  autumn. 

The  autumn  colors  are  due  to  intermingled  shades  of 
green,  yellow,  and  red.  The  coloration  varies  with  the  kind 
of  plant,  the  special  location,  and  the  season.  Even  in  the 
same  species  or  kind,  individual  plants  differ  in  color  ;  and 
this  individuality  usually  distinguishes  the  plant  year  by 
year.  That  is,  an  oak  which  is  maroon  red  this  autumn  is 
likely  to  exhibit  that  range  of  color  every  year.  The  au- 
tumn color  is  associated  with  the  natural  maturity  and 
death  of  the  leaf,  but  it  is  most  brilliant  in  long  and  open 


14  PLANT  BIOLOGY 

falls  —  largely  because  the  foliage  ripens  more  gradually 
and  persists  longer  in  such  seasons.  It  is  probable  that 
the  autumn  tints  arc  of  no  utility  to  the  plant.  Autumn 
colors  arc  not  caused  by  frost.  Because  of  the  long,  dry 
falls  and  the  great  variety  of  plants,  the  autumnal  color  of 
the  American  landscape  is  phenomenal. 

Ecology. — The  study  of  the  relationships  of  plants  and 
animals  to  each  other  and  to  seasons  and  environments  is 
known  as  ecology  (still  written  cecology  in  the  dictionaries). 
It  considers  the  habits,  habitats,  and  modes  of  life  of  liv- 
ing things  —  the  places  in  which  they  grow,  how  they 
migrate  or  are  disseminated,  means  of  collecting  food, 
their  times  and  seasons  of  flowering,  producing  young, 
and  the  like. 

Suggestions.  —  One  of  the  best  of  all  subjects  for  school  instruc- 
tion in  botany  is  the  study  of  plant  societies.  It  adds  definiteness 
and  zest  to  excursions.  7.  Let  each  excursion  be  confined  to  one 
or  two  societies.  Visit  one  day  a  swamp,  another  day  a  forest, 
another  a  pasture  or  meadow,  another  a  roadside,  another  a  weedy 
field,  another  a  cliff  or  ravine.  Visit  shores  whenever  possible. 
\J  Each  pupil  should  be  assigned  a  bit  of  ground  —  say  10  or  20  ft. 
square  —  for  special  study.  He  should  make  a  list  showing  (1) 
how  many  kinds  of  plants  it  contains,  (2)  the  relative  abundance 
of  each.  The  lists  secured  in  different  regions  should  be  com- 
pared. It  does  not  matter  greatly  if  the  pupil  does  not  know  all 
the  plants.  He  may  count  the  kinds  without  knowing  the  names. 
It  is  a  good  plan  for  the  pupil  to  make  a  dried  specimen  of  each 
kind  for  reference.  The  pupil  should  endeavor  to  discover  why 
the  plants  grow  as  they  do.  Note  what  kinds  of  plants  grow  next 
each  other  ;  and  which  are  undergrowth  and  which  overgrowth  ; 
and  which  are  erect  and  which  wide-spreading.  Challenge  every 
plant  society. 


CHAPTER  V 

THE   PLANT    BODY 

The  Parts  of  a  Plant.  —  Our  familiar  plants  are  made  up 
of  several  distinct  parts.  The  most  prominent  of  these 
parts  are  root,  stem,  leaf,  flower,  fruit,  and  seed.  Familiar 
plants  differ  wonderfully  in  size  and  shape,  —  from  fragile 
mushrooms,  delicate  waterweeds  and  pond-scums,  to  float- 
ing leaves,  soft  grasses,  coarse  weeds,  tall  bushes,  slender 
climbers,  gigantic  trees,  and  hanging  moss. 

The  Stem  Part.  —  In  most  plants  there  is  a  main  central 
part  or  shaft  on  which  the  other  or  secondary  parts  are 
borne.  This  main  part  is  the  plant  axis.  Above  ground, 
in  most  plants,  the  main  plant  axis  bears  the  brandies, 
leaves,  and  flowers ;  below  ground,  it  bears  the  roots. 

The  rigid  part  of  the  plant,  which  persists  over  winter 
and  which  is  left  after  leaves  and  flowers  are  fallen,  is  the 
framework  of  the  plant.  The  framework  is  composed  of 
both  root  and  stem.  When  the  plant  is  dead,  the  frame- 
work remains  for  a  time,  but  it  slowly  decays.  The  dry 
winter  stems  of  weeds  are  the  framework,  or  skeleton  of 
the  plant  (Figs,  u  and  12).  The  framework  of  trees  is 
the  most  conspicuous  part  of  the  plant. 

The  Root  Part.  —  The  root  bears  the  stem  at  its  apex, 
but  otherwise  it  normally  bears  only  root-branches.  The 
stem,  however,  bears  leaves,  flowers,  and  fruits.  Those 
living  surfaces  of  the  plant  which  are  most  exposed  to 
light  are  green  or  highly  colored.  The  root  tends  to  grow 
downward,  but  the  stem  tends  to  grow  upward  toward  light 

•5 


i6 


PLANT  BIOLOGY 


.     * 


and  air.     The  plant  is  anchored  or  fixed  in  the  soil  by  the 

roots.     Plants  have  been  called  "earth  parasites." 

The  Foliage  Part.  —  The  leaves  precede  the  flowers  in 

point  of  time  or  life  of  the  plant.       The  flowers  always 

precede  the  fruits  and  seeds.    Many  plants  die  when  the 

seeds  have  matured.     The  whole  mass  of  leaves  of  any 

plant  or  any  branch  is 

known    as    its  foliage. 

In    some    cases,   as    in 

crocuses,    the    flowers 

seem    to    precede    the 

leaves ;  but  the  leaves 

that  made  the  food  for 

these  flowers  grew  the 

preceding  year. 

The  Plant  Generation. 

—  The     course     of     a 

plant's  life,  with  all  the 

events    through  which 

the      plant      naturally 

passes,    is    known     as 

the  plant's  life-history. 

The     life-history     em- 

Fig.  ii.  — Plant  of  a      Fig.  12.  — Frame-    braces    various    Stages, 
Wild  Sunflower.  work  of  Fig.  ii. 

or  epochs,  as  dormant 

seed,  germination, growth,  flowering,  fruiting.    Some  plants 

run  their  course  in  a  few  weeks  or  months,  and  some  live 

for  centuries. 

The  entire  life-period  of  a  plant  is  called  a  generation. 
It  is  the  whole  period  from  birth  to  normal  death,  without 
reference  to  the  various  stages  or  events  through  which  it 
passes. 

A  generation  begins  with  the  young  seed,  not  with  germi- 


THE  PLANT  BODY  1 7 

nation.  //  ends  with  death  —  that  is,  when  no  life  is  left 
in  any  part  of  the  plant,  and  only  the  seed  or  spore 
remains  to  perpetuate  the  kind.  In  a  bulbous  plant,  as  a 
lily  or  an  onion,  the  generation  does  not  end  until  the  bulb 
dies,  even  though  the  top  is  dead. 

When  the  generation  is  of  only  one  season's  duration, 
the  plant  is  said  to  be  annual.  When  it  is  of  two  seasons, 
it  is  biennial.  Biennials  usually  bloom  the  second  year. 
When  of  three  or  more  seasons,  the  plant  is  perennial. 
Examples  of  annuals  are  pigweed,  bean,  pea,  garden  sun- 
flower ;  of  biennials,  evening  primrose,  mullein,  teasel ;  of 
perennials,  dock,  most  meadow  grasses,  cat-tail,  and  all 
shrubs  and  trees. 

Duration  of  the  Plant  Body.  —  Plant  structures  which 
are  more  or  less  soft  and  which  die  at  the  close  of  the 
season  are  said  to  be  herbaceous,  in  contradistinction  to 
being  ligneous  or  woody.  A  plant  which  is  herbaceous  to 
the  ground  is  called  an  herb;  but  an  herb  may  have  a 
woody  or  perennial  root,  in  which  case  it  is  called  an 
herbaceous  perennial.  Annual  plants  are  classed  as  herbs. 
Examples  of  herbaceous  perennials  are  buttercups,  bleed- 
ing heart,  violet,  water  lily,  Bermuda  grass,  horse-radish, 
dock,  dandelion,  golden  rod,  asparagus,  rhubarb,  many 
wild  sunflowers  (Figs,  n,  12). 

Many  herbaceous  perennials  have  short  generations. 
They  become  weak  with  one  or  two  seasons  of  flowering 
and  gradually  die  out.  Thus,  red  clover  usually  begins  to 
fail  after  the  second  year.  Gardeners  know  that  the  best 
bloom  of  hollyhock,  larkspur,  pink,  and  many  other  plants, 
is  secured  when  the  plants  are  only  two  or  three  years 
old. 

Herbaceous  perennials  which  die  away  each  season  to 
bulbs  or  tubers,  are  sometimes  called  pseud-annuals  (that 
c 


i8 


PLANT  BIOLOGY 


is,  false  annuals).     Of  such  are  lily,  crocus,  onion,  potato, 
bull  nettle,  and  false  indigo  of  the  Southern  states. 

True  annuals  reach  old  age  the  first  year.  Plants  which 
are  normally  perennial  may  become  annual  in  a  shorter- 
season  climate  by  being  killed  by  frost,  rather  than  by  dying 
naturally  at  the  end  of  a  season  of  growth.  They  are  cli- 
matic annuals.  Such  plants  are  called  plur-annuals  in  the 
short-season  region.     Many  tropical  perennials  are   plur- 


Fig.  13.  —  A  Shrub  or  Bush.     Dogwood  osier. 

annuals  when  grown  in  the  north,  but  they  are  treated  as 
true  annuals  because  they  ripen  sufficient  of  their  crop  the 
same  season  in  which  the  seeds  are  sown  to  make  them 
worth  cultivating,  as  tomato,  red  pepper,  castor  bean, 
cotton.  Name  several  vegetables  that  are  planted  in 
gardens  with  the  expectation  that  they  will  bear  till  frost 
comes. 

Woody  or  ligneous  plants  are  usually  longer  lived  than 
herbs.      Those  that  remain   low  and   produce  several   or 


THE  PLANT  BODY 


19 


many  similar  shoots  from  the 
base  are  called  shrubs,  as  lilac, 
rose,  elder,  osier(Fig.  13).  Low 
and  thick  shrubs  are  bushes. 
Plants  that  produce  one  main 
trunk  and  a  more  or  less  elevated 
head  are  trees  (Fig.  14).  All 
shrubs  and  trees  are  perennial. 
Every  plant  makes  an  effort 
to  propagate,  or  to  perpetuate  its 
kind ;  and,  as  far  as  we  can 
see,  this  is  the  end  for  which 
the  plant  itself  lives.  The  seed 
or  spore  is  the  final  product  of 
the  plant. 


^  Willi 

Fig.  14. —  A  Tree.    The  weeping 
birch. 


Suggestions.  —  8.  The  teacher  may  assign  each  pupil  to  one 
plant  in  the  school  yard,  or  field,  or  in  a  pot,  and  ask  him  to  bring 
out  the  points  in  the  lesson.  9.  The  teacher  may  put  on  the 
board  the  names  of  many  common  plants  and  ask  the  pupils  to 
classify  into  annuals,  pseud-annuals,  plur-annuals  (or  climatic 
annuals),  biennials,  perennials,  herbaceous  perennials,  ligneous 
perennials,  herbs,  bushes,  trees.  Every  plant  grown  on  the  farm 
should  be  so  classified  :  wheat,  oats,  corn,  buckwheat,  timothy, 
strawberry,  raspberry,  currant,  tobacco,  alfalfa,  flax,  crimson  clover, 
hops,  covvpea,  field  bean,  sweet  potato,  peanut,  radish,  sugar-cane, 
barley,  cabbage,  and  others.  Name  all  the  kinds  of  trees  you 
know. 


CHAPTER   VI 

SEEDS   AND   GERMINATION 

The  seed  contains  a  miniature  plant,  or  embryo.  The 
embryo  usually  has  three  parts  that  have  received 
names  :  the  stemlet,  or  caulicle ;  the  seed-leaf,  or  cotyledon 
(usually  i  or  2);  the  bud,  or  plumule,  lying  between  or 
above  the  cotyledons.  These  parts  are  well 
seen  in  the  common  bean  (Fig.  15),  particu- 
larly when  the  seed  has  been  soaked  for  a 

few  hours.     One  of  the  large  cotyledons  — 
Fig.  15.  — Parts  .  . 

of  the  bean.      comprising  half  of  the  bean  —  is  shown  at 

/?,  cotyledon-,  o,  R.  The  caulicle  is  at  O.  The  plumule  is 
mule-  e'jr,'  first  shown  at  A.  The  cotyledons  are  attached 
node-  to  the  caulicle  at  F:  this  point  may  be  taken 

as  the  first  node  or  joint. 

The  Number  of  Seed-leaves.  —  All  plants  having  two 
seed-leaves  belong  to  the  group  called  dicotyledons.  Such 
seeds  in  many  cases  split  readily  in  halves,  e.g.  a  bean. 
Some  plants  have  only  one  seed-leaf  in  a  seed.  They 
form  a  group  of  plants  called  monocotyledons.  Indian 
corn  is  an  example  of  a  plant  with  only  one  seed-leaf : 
a  grain  of  corn  does  not  split  into  halves  as  a  bean  does. 
Seeds  of  the  pine  family  contain  more  than  two  cotyledons, 
but  for  our  purposes  they  may  be  associated  with  the  dicoty- 
ledons, although  really  forming  a  different  group. 

These  two  groups — the  dicotyledons  and  the  mono- 
cotyledons —  represent  two  great  natural  divisions  of  the 
vegetable  kingdom.     The  dicotyledons  contain  the  woody 

20 


SEEDS  AND    GERMINATION  2 1 

bark-bearing  trees  and  bushes  (except  conifers),  and  most 
of  the  herbs  of  temperate  climates  except  the  grasses, 
sedges,  rushes,  lily  tribes,  and  orchids.  The  flower-parts 
are  usually  in  fives  or  multiples  of  five,  the  leaves  mostly 
netted-veined,  the  bark  or  rind  distinct,  and  the  stem  often 
bearing  a  pith  at  the  center.  The  monocotyledons  usually 
have  the  flower-parts  in  threes  or  multiples  of  three,  the 
leaves  long  and  parallel-veined,  the  bark  not  separable, 
and  the  stem  without  a  central  pith. 

Every  seed  is  provided  with  food  to  support  the  germinat- 
ing plant.  Commonly  this  food  is  starch.  The  food  may 
be  stored  in  the  cotyledons,  as  in  bean,  pea,  squash  ;  or  out- 
side the  cotyledons,  as  in  castor  bean,  pine,  Indian  corn. 
When  the  food  is  outside  or  around  the  embryo,  it  is 
usually  called  endosperm. 

Seed-coats;  Markings  on  Seed. — The  embryo  and  en- 
dosperm are  inclosed  within  a  covering  made  of  two  or 
more  layers  and  known  as  the  seed-coats. 
Over  the  point  of  the  caulicle  is  a  minute 
hole  or  a  thin  place  in  the  coats  known  as 
the  micropyle.  This  is  the  point  at  which  fig.i6.— exter- 
the  pollen-tube  entered  the  forming  ovule  nal  parts  of 
and  through  which  the  caulicle  breaks  in 
germination.  The  micropyle  is  shown  at  M  in  Fig.  16. 
The  scar  where  the  seed  broke  from  its  funiculus  (or  stalk 
that  attached  it  to  its  pod)  is  named  the  hilum.  It  occu- 
pies a  third  of  the  length  of  the  bean  in  Fig.  16.  The 
hilum  and  micropyle  are  always  present  in  seeds,  but  they 
are  not  always  close  together.  In  many  cases  it  is  difficult 
to  identify  the  micropyle  in  the  dormant  seed,  but  its  loca- 
tion is  at  once  shown  by  the  protruding  caulicle  as  germi- 
nation begins.  Opposite  the  micropyle  in  the  bean  (at  the 
other  end  of  the  hilum)  is  an  elevation  known  as  the  raphe. 


22  PLANT  BIOLOGY 

This  is  formed  by  a  union  of  the  funiculus,  or  seed-stalk, 
with  the  seed-coats,  and  through  it  food  was  transferred 
for  the  development  of  the  seed,  but  it  is  now  functionless. 

Seeds  differ  wonderfully  in  size,  shape,  color,  and  other 
characteristics.  They  also  vary  in  longevity.  These 
characteristics  are  peculiar  to  the  species  or  kind.  Some 
seeds  maintain  life  only  a  few  weeks  or  even  days,  whereas 
others  will  "keep"  for  ten  or  twenty  years.  In  special 
cases,  seeds  have  retained  vitality  longer  than  this  limit, 
but  the  stories  that  live  seeds,  several  thousand  years  old, 
have  been  taken  from  the  wrappings  of  mummies  are  un- 
founded. 

Germination.  —  The  embryo  is  not  dead  ;  it  is  only  dor- 
L-  mant.  When  supplied  with  moisture,  warmth,  and  oxygen 
{air),  it  azvakes  and  grows:  this  growth  is  germination. 
The  embryo  lives  for  a  time  on  the  stored  food,  but  gradu- 
ally the  plantlet  secures  a  foothold  in  the  soil  and  gathers 
food  for  itself.  When  the  plantlet  is  finally  able  to  shift 
for  itself,  germination  is  complete. 

Early  Stages  of  Seedling.  —  The  germinating  seed  first 
absorbs  zvater,  and  swells.  The  starchy  matters  gradually 
become  soluble.  The  seed-coats  are  ruptured,  the  caulicle 
and  plumule  emerge.  During  this  process  the  seed 
respires  freely,  throzving  off  carbon  dioxid  (C02). 

The  caulicle  usually  elongates,  and  from  its  lower  end 
roots  are  emitted.  The  elongating  caulicle  is  known  as 
the  hypocotyl  ("below  the  cotyledons").  That  is,  the 
hypocotyl  is  that  part  of  the  stem  of  the  plantlet  lying 
between  the  roots  and  the  cotyledon.  The  general  direc- 
tion of  the  young  hypocotyl,  or  emerging  caulicle,  is  down- 
wards. As  soon  as  roots  form,  it  becomes  fixed  and  its 
subsequent  growth  tends  to  raise  the  cotyledons  above  the 
ground,  as  in  the  bean.     When  cotyledons  rise   into  the 


SEEDS  AND    CERMLXATION 


^ 


Fir,.  17.  —  Pea.  Grotesque  forms  assumed 
when  the  roots  cannot  gain  entrance  to 
the  soil. 


air,  germination  is  said  to  be  epigeal  ("above  the  earth"). 
Bean  and  pumpkin  are  examples.  When  the  hypocotyl 
does   not  elongate  greatly  ,- 

and  the  cotyledons  remain 
under  ground,  the  germi- 
nation is  hypogeal  ("be- 
neath the  earth").  Pea 
and  scarlet  runner  bean 
are  examples  (Fig.  48). 
When  the  germinating 
seed  lies  on  a  hard  sur- 
face, as  on  closely  com- 
pacted soil,  the  hypocotyl 
and  rootlets  may  not  be  able  to  secure  a  foothold  and  they  4^ 
assume  grotesque  forms.  (Fig.  17.)  Try  this  with  peas  ^ 
and  beans. 

The  first  internode  ("  between  nodes")  above  the  coty- 
ledons is  the  epicotyl.     It  elevates  the  plumule  into  the 
air,  and  the  plumule-leaves  expand  into  the  first  true  leaves 
of  the  plant.     These  first  true  leaves,  however,  may  be       t— 
very  unlike  the  later  leaves  in  shape. 

Germination  of  Bean.  —  The  common  bean,  as  we  have 
seen  (Fig.  15),  has  cotyledons  that  occupy  all  the  space 
inside  the  seed-coats.  When  the  hy- 
pocotyl, or  elongated  caulicle,  emerges, 
the  plumule-leaves  have  begun  to  en- 
large, and  to  unfold  (Fig.  18).  The 
hypocotyl  elongates  rapidly.  One  end 
of  it  is  held  by  the  roots.  The  other 
is  held  by  the  seed-coats  in  the  soil. 
It  therefore  takes  the  form  of  a  loop, 
and  the  central  part  of  the  loop  "  comes  up  "  first  (a,  Fig. 
19).     Presently  the  cotyledons  come  out  of  the  seed-coats, 


Fig.  18.  —  Cotyledons 
of  Germinating 
Bean  spread  apart 
to  show  Elongat- 
ing Caulicle  and 
Plumule. 


PLANT  BIOLOGY 

and  the  plant  straightens  and  the 
cotyledons  expand.  These  coty- 
ledons, or  "  halves  of  the  bean," 
persist  for  some  time  (/;,  Fig. 
19).  They  often  become  green 
and  probably  perform  some 
function  of  foliage.  Because  of 
its  large  size,  the  Lima  bean 
shows  all  these  parts  well. 

Germination  of  Castor  Bean.  — 
In  the  castor  bean  the  hilum 
and  micropyle  are  at  the  smaller  end 
(Fig.  20).  The  bean  "  comes  up"  with  a 
loop,  which  indicates  that  the  hypocotyl 
greatly  elongates.  On  examining  germi- 
nating seed,  however,  it  will  be  found 
that  the  cotyledons  are  contained  inside  a  fleshy  body, 
or  sac  (a,  Fig.  21).  This  sac  is  the  endosperm.  Against 
its  inner  surface  the  thin,  veiny  coty- 
ledons are  very  closely  pressed,  ab- 


FlG.    19. 


•  Germination  of 

Bean. 


Fig.  20.  —  Sprout- 
ing of  Castor 
Bean. 


Fig.  21. —  Germina- 
tion of  Castor  Bean. 

Endosperm  at  a. 


Fig.  22.—  Castor 
Bean. 

Endosperm  at  a,  a;  coty- 
ledons at  i. 


Fig.  23.  —  Germination 
Complete  in  Castor 
Bean. 


sorbing  its  substance  (Fig.  22).  The  cotyledons  increase 
in  size  as  they  reach  the  air  (Fig.  23),  and  become  func- 
tional leaves. 


SEEDS  AND    GERMINATION 


25 


Germination  of  Monocotyledons.  —  Thus  far  we  have  stud- 
ied dicotyledonous  seeds  ;  we  may  now  consider  the  mono- 
cotyledonous  group.  Soak  kernels  of  corn.  Note  that 
the  micropyle  and  hilum  are  at  the  smaller  end  (Fig.  24). 
Make  a  longitudinal  section  through  the 
narrow  diameter;    Fig.  25  shows  it.     The 


Fig.  24. — Sprout- 
ing Indian  Corn. 

Hilum  at  A;   micro- 
pyle at  d. 


Fig.  25. —  Kernel 
of  Indian  Corn. 

Caulicle  at  b;  cotyle- 
don at  a ;  plumule 
at  /. 


Fig.  26.— Indian 
Corn. 

Caulicle  at  c;    roots  emerging  at 
;«;   plumule  at/. 


single  cotyledon  is  at  a,  the  caulicle   at   b,  the   plumule 
at/.     The  cotyledon  remains  in  the  seed.     The  food  is 
stored  both  in  the  cotyledon  and  as  endosperm,  chiefly  the 
latter.     The  emerging  shoot  is  the  plumule,  with  a  sheath- 
ing leaf  (p,  Fig.  26).     The  root  is  emitted  from  the  tip  of 
»      the  caulicle,  c.      The  caulicle  is  held  in  a  sheath 
(formed  mostly  from  the  seed-coats),  and  some  of 
the   roots    escape    through   the    upper   end 
of  this  sheath  (m,  Fig.  26).     The 
epicotyl   elongates,   particularly    if 
the  seed  is  planted 
*\  _/s,==av —      deep     or    if    it    is 
kept    for    a    time 
confined.     In  Fig. 
27  the  epicotyl  has 
elongated  from  n  to  p.     The  true  plumule-leaf  is  at  o,  but 
other  leaves  grow  from  its  sheath.      In  Fig.  28  the  roots 
are    seen    emerging   from  the   two   ends,  of _the   caulicle- 


Fig.  27. —  Indian  Corn. 

o,  plumule;   n  to/,  epicotyl. 


26 


PLANT   HIOI.OGY 


sheath,  c\  m\  the  epicoty]  has  grown   to/;   the  first  plu- 
mule-leaf is  at  o. 

In  studying  corn  or  other  fruits  or  seeds,  the  pupil  should 
note  how  the  seeds  are  arranged,  as  on  the  cob.     Count  the 

rows  on  a  corn  cob.  Odd  or 
even  in  number  ?  Always  the 
same  number?  The  silk  is 
the  style :  find  where  it  was 
attached  to  the  kernel.  Did 
the  ear  have  any  coverings  ? 
Explain.  Describe  colors  and 
markings  of  kernels  of  corn ; 
and  of  peas,  beans,  castor 
bean. 

Gymnosperms.  —  The  seeds 
in  the  pine  cone,  not  being 
inclosed  in  a  seed-vessel, 
readily  fall  out  when  the  cone 
dries  and  the  scales  separate. 
Hence  it  is  difficult  to  find 
cones  with  seeds  in  them  after 
autumn  has  passed  (Fig.  29). 
The  cedar  is  also  a  gymno- 
sperm. 

Remove  a  scale  from  a 
pine  cone  and  draw  it  and 
the  seeds  as  they  lie  in  place 
on  the  upper  side  of  the  scale. 
Examine  the  seed,  preferably  with  a  magnifying  glass.  Is 
there  a  hilum  ?  The  micropyle  is  at  the  bottom  or  little 
end  of  the  seed.  Toss  a  seed  upward  into  the  air.  Why 
does  it  fall  so  slowly  ?  Can  you  explain  the  peculiar  whirl- 
ing motion  by  the  shape  of  the  wing  ?      Repeat  the  ex- 


Fig.  28. 


■Germination  is  Com- 
plete. 


/,  top  of  epicotyl;'o,  plumule-leaf; 
tn,  roots;  c,  lower  roots. 


SEEDS  AND    GERMINA  TION 


27 


periment  in  the  wind.  Remove  the 
wing  from  a  seed  and  toss  it  and  an 
uninjured  seed  into  the  air  together. 
What  do  you  infer  from  these  ex- 
periments ? 

Suggestions.  —  Few  subjects  con- 1 
nected  with  the  study  of  plant-life  are  sot 
useful  in  schoolroom  demonstrations  as 
germination.  The  pupil  should  prepare 
the  soil,  plant  the  seeds,  water  them,  and 
care  for  the  plants.  10.  Plant  seeds  in 
pots  or  shallow  boxes.  The  box  should 
not  be  very  wide  or  long,  and  not  over 
four  inches  deep.  Holes  may  be  bored 
in  the  bottom  so  it  will  not  hold  water. 
Plant  a  number  of  squash,  bean,  corn, 
pine,  or  other  seeds  about  an  inch  deep 
in  damp  sand  or  pine  sawdust  in  this 
box.  The  depth  of  planting  should  be 
two  to  four  times  the  diameter  of  the 
seeds.  Keep  the  sand  or  sawdust  moist 
but  not  wet.  If  the  class  is  large,  use 
several  boxes,  that  the  supply  of  speci- 
mens may  be  ample.  Cigar  boxes  and 
chalk  boxes  are  excellent  for  individual 
pupils.  It  is  well  to  begin  the  planting 
of  seeds  at  least  ten  days  in  advance  of 
the  lesson,  and  to  make  four  or  five  differ- 
ent plantings  at  intervals.  A  day  or  two 
before  the  study  is  taken  up,  put  seeds 
to  soak  in  moss  or  cloth.  The  pupil 
then  has  a  series  from  swollen  seeds  to 
complete  germination,  and  all  the  steps  can  be  made  out.  Dry 
seeds  should  be  had  for  comparison.  If  there  is  no  special  room 
for  laboratory,  nor  duplicate  apparatus  for  every  pupil,  each  ex- 
periment may  be  assigned  to  a  committee  of  two  pupils  to  watch 
in  the  schoolroom.  11.  Good  seeds  for  study  are  those  detailed 
in  the  lesson,  and  buckwheat,  pumpkin,  cotton,  morning  glory, 
radish,  four  o'clock,  oats,  wheat.  It  is  best  to  use  familiar  seeds 
of  farm  and  garden.  Make  drawings  and  notes  of  all  the  events 
in  the  germination.  Note  the  effects  of  unusual  conditions,  as 
planting  too  deep  and  too  shallow  and  different  sides  up.  For 
hypogeal  germination,  use  the  garden  pea,  scarlet  runner  or  Dutch 


Fig.  29.  —  Coxes  of  Hem- 
lock (above),  White 
Pine,  Pitch  Pine. 


28  PLANT  BIOLOGY 

case-knife  bean,  acorn,  horse-chestnut.  Squash  seeds  are  excellent 
for  germination  studies,  because  the  cotyledons  become  green  and 
leafy  and  germination  is  rapid.  Its  germination,  as  also  that  of  the 
scarlet  runner  bean,  is  explained  in  "Lessons  with  Plants."  Onion 
is  excellent,  except  that  it  germinates  too  slowly.  In  order  to  study 
the  root  development  of  germinating  plantlets,  it  is  well  to  pro- 
vide a  deeper  box  with  a  glass  side  against  which  the  seeds  are 
planted.  12.  Observe  the  germination  of  any  common  seed 
about  the  house  premises.  When  elms,  oaks,  pines,  or  maples  are 
abundant,  the  germination  of  their  seeds  may  be  studied  in  lawns 
and  along  fences.  13.  When  studying  germination,  the  pupil 
should  note  the  differences  in  shape  and  size  between  cotyledons 
and  plumule-leaves,  and  between  plumule-leaves  and  the  normal 
leaves  (Fig.  30).     Make  drawings.     14.    Make  the  tests  described 

in    the    introductory    experi- 
gff*"  '       *iss\      <""\        rnents  with   bean,  corn,   the 

castor  bean,  and  other  seed 

for  starch  and  proteids.    Test 

flour,  oatmeal,  rice,  sunflower, 

fi^^^iki&t*.  -oj*^  f°ur  o'clock,  various  nuts,  and 

flNl^ ■5^&*£*^n  C ^"^-  any   other   seeds    obtainable. 

Record   your  results   by  ar- 
Fig.  30. —  Muskmelox  Seedlings,  with      ranging    the    seeds    in    three 

the  unlike  seed-leaves  and  true  leaves.  classes,   I.  Much  Starch  (color 

blackish  or  purple),  2.  Little 
starch  (pale  blue  or  greenish),  3.  No  starch  (brown  or  yellow). 
15.  Rate  of  growth  of  seedlings  as  affected  by  differences  in  tempera- 
ture. Pack  soft  wet  paper  to  the  depth  of  an  inch  in  the  bottom 
of  four  glass  bottles  or  tumblers.  Put  ten  soaked  peas  or  beans  into 
each.  Cover  each  securely  and  set  them  in  places  having  different 
temperatures  that  vary  little.  (A  furnace  room,  a  room  with  a 
stove,  a  room  without  stove  but  reached  by  sunshine,  an  unheated 
room  not  reached  by  the  sun.)  Take  the  temperatures  occasion- 
ally with  a  thermometer  to  find  difference  in  temperature.  The 
tumblers  in  warm  places  should  be  covered  very  tightly  to  prevent 
the  germination  from  being  retarded  by  drying  out.  Record  the 
number  of  seeds  which  sprout  in  each  tumbler  within  1  day  ;  2  days  ; 
3  days  ;  4  days,  etc.  16.  Is  air  necessary  for  the  germination  and , 
growth  of  seedlings  ?  Place  damp  blotting  paper  in  the  bottom  of  a 
bottle  and  fill  it  three  fourths  full  of  soaked  seeds,  and  close  it 
tightly  with  a  rubber  stopper  or  oiled  cork.  Prepare  a  "  check 
experiment"  by  having  another  bottle  with  all  conditions  the  same 
except  that  it  is  covered  loosely  that  air  may  have  access  to  it, 
and  set  the  bottles  side  by  side  (why  keep  the  bottles  together?). 
Record  results  as  in  the  preceding  experiment.     17.    What  is-  the 


SEEDS  AND    GERMINATION  29 

nature  of  the  gas  given  off  by  germinating  seeds  ?  Fill  a  tin  box  or 
large-necked  bottle  with  dry  beans  or  peas,  then  add  water ;  note 
how  much  they  swell.  Secure  two  fruit-jars.  Fill  one  of  them  a 
third  full  of  beans  and  keep  them  moist.  Allow  the  other  to  remain 
empty.  In  a  day  or  two  insert  a  lighted  splinter  or  taper  into 
each.  In  the  empty  jar  the  taper  burns  :  it  contains  oxygen. 
In  the  seed  jar  the  taper  goes  out :  the  air  has  been  replaced 
by  carbon  dioxid.  The  air  in  the  bottle  may  be  tested  for 
carbon  dioxid  by  removing  some  of  it  with  a  rubber  bulb  attached 
to  a  glass  tube  (or  a  fountain-pen  filler)  and  bubbling  it  through 
lime  water.  18.  Temperature.  Usually  there  is  a  perceptible 
rise  in  temperature  in  a  mass  of  germinating  seeds.  This  rise  may 
be  tested  with  a  thermometer.  19.  hiterior  of  seeds.  Soak 
seeds  for  twenty-four  hours  and  remove  the  coat.  Distinguish 
the  embryo  from  the  endosperm.  Test  with  iodine.  20.  Of 
what  utility  is  the  food  in  seeds  ?  Soak  some  grains  of  corn 
overnight  and  remove  the  endosperm,  being  careful  not  to 
injure  the  fleshy  cotyledon.  Plant  the  incomplete  and  also  some 
complete  grains  in  moist  sawdust  and  measure  their  growth  at 
intervals.  (Boiling  the  sawdust  will  destroy  molds  and  bacteria 
which  might  interfere  with  experiment.)  Peas  or  beans  may  be 
sprouted  on  damp  blotting  paper ;  the  cotyledons  of  one  may  be 
removed,  and  this  with  a  normal  seed  equally  advanced  in  germi- 
nation may  be  placed  on  a  perforated  cork  floating  in  water  in 
a  jar  so  that  the  roots  extend  into  the  water.  Their  growth 
may  be  observed  for  several  weeks.  21.  Effect  of  darkness  on  - 
seeds  and  seedlings.  A  box  may  be  placed  mouth  downward 
over  a  smaller  box  in  which  seedlings  are  growing.  The  empty 
box  should  rest  on  half-inch  blocks  to  allow  air  to  reach  the 
seedlings.  .  Note  any  effects  on  the  seedlings  of  this  cutting  off 
of  the  light.  Another  box  of  seedlings  not  so  covered  may 
be  used  for  a  check.  Lay  a  plank  on  green  grass  and  after  a 
week  note  the  change  that  takes  place  beneath  it.  22.  Seedling 
of  pine.  Plant  pine  seeds.  Notice  how  they  emerge.  Do  the 
cotyledons  stay  in  the  ground  ?  How  many  cotyledons  have 
they  ?  When  do  the  cotyledons  get  free  from  the  seed-coat  ? 
What  is  the  last  part  of  the  cotyledon  to  become  free  ?  Where  is 
the  growing  point  or  plumule  ?  How  many  leaves  appear  at 
once  ?  Does  the  new  pine  cone  grow  on  old  wood  or  on  wood 
formed  the  same  spring  with  the  cone?  Can  you  always  find 
partly  grown  cones  on  pine  trees  in  winter?  Are  pine  cones 
when  mature  on  two-year-old  wood  ?  How  long  do  cones  stay 
on  a  tree  after  the  seeds  have  fallen  out  ?  What  is  the  advantage 
of  the  seeds  falling  before  the  cones?  23.  Home  experiments. 
If  desired,    nearly   all   of  the    foregoing   experiments    may    be 


So 


PLANT  BIOLOGY 


Fig.  31.  —  A  Home-made 
Seed-tester. 


tried  at  home.  The  pupil  can  thus  make  the  drawings  for  the 
notebook  at  home.  A  daily  record  of  measurements  of  the  change 
in  size  of  the  various  parts  of  the  seedling  should  also  be  made. 
24.  Seed-testing.  —  It  is  important  that  one  know  before  planting 
whether  seeds  are  good,  or  able  to  grow.  A  simple  seed-tester 
may  be  made  of  two  plates,  one  inverted  over  the  other  (Fig.  31). 
The  lower  plate  is  nearly  filled  with  clean 
sand,  which  is  covered  with  cheese  cloth 
or  blotting  paper  on  which  the  seeds  are 
placed.  Canton  flannel  is  sometimes 
used  in  place  of  sand  and  blotting  paper. 
The  seeds  are  then  covered  with  another 
blotter  or  piece  of  cloth,  and  water  is 
applied  until  the  sand  and  papers  are 
saturated.  Cover  with  the  second  plate. 
Set  the  plates  where  they  will  have  about 
the  temperature  that  the  given  seeds 
would  require  out  of  doors,  or  perhaps  a 
slightly  higher  temperature.  Place  100  or  more  grains  of  clover, 
corn,  wheat,  oats,  rye,  rice,  buckwheat,  or  other  seeds  in  the  tester, 
and  keep  record  of  the  number  that  sprout.  The  result  will  give 
a  percentage  measure  of  the  ability  of  the  seeds  to  grow.  Note 
whether  all  the  seeds  sprout  with  equal  vigor  and  rapidity.  Most 
seeds  will  sprout  in  a  week  or  less.  Usually  such  a  tester  must 
have  fresh  sand  and  paper  after  every  test,  for  mold  fungi  are  likely 
to  breed  in  it.  If  canton  flannel  is  used,  it  may  be  boiled.  If 
possible,  the  seeds  should  not  touch  each  other. 

Note  to  Teacher.  —  With  the  study  of  germination,  the  pupil 
will  need  to  begin  dissecting. 

For  dissecting,  one  needs  a  lens  for  the  examination  of  the 
smaller  parts  of  plants  and  animals.  It  is  best  to  have  the  lens 
mounted  on  a  frame,  so  that  the  pupil  has  both  hands  free  for 
pulling  the  part  in  pieces.  An  ordinary  pocket  lens  may  be 
mounted  on  a  wire  in  a  block,  as  in  Fig.  A.  A  cork  is  slipped  on 
the  top  of  the  wire  to  avoid  injury  to  the  face.  The  pupil  should 
be  provided  with  two  dissecting  needles  (Fig.  B),  made  by 
securing  an  ordinary  needle  in  a  pencil-like  stick.  Another  con- 
venient arrangement  is  shown  in  Fig.  C.  A  small  tin  dish  is  used 
for  the  base.  Into  this  a  stiff  wire  standard  is  soldered.  The 
dish  is  filled  with  solder,  to  make  it  heavy  and  firm.  Into  a  cork 
slipped  on  the  standard,  a  cross  wire  is  inserted,  holding  on  the 
end  a  jeweler's  glass.  The  lens  can  be  moved  up  and  down  and 
sidewise.  This  outfit  can  be  made  for  about  seventy-five  cents. 
Fig.  D  shows   a   convenient   hand-rest   or  dissectine-stand  to  be 


SEEDS  AND    GERMINATION 


31 


used  under  this  lens.     It  may  be  16  in.  long,  4  in.  high,  and  4  or  5 

in.  broad. 

Various  kinds  of  dissecting  microscopes  are  on  the  market,  and 
these  are  to  be  recommended  when  they  can  be  afforded. 


B.  —  Dis- 
secting 
Needle 
%  natural 
size. 


D.—  Dissecting  Stand. 


Dissecting  Glass. 


^.  —  Improvised 
Stand  for  Lens. 


Instructions  for  the  use  of  the  compound  microscope,  with 
which  some  schools  may  be  equipped,  cannot  be  given  in  a  brief 
space  ;  the  technique  requires  careful  training.  Such  microscopes 
are  not  needed  unless  the  pupil  studies  cells  and  tissues. 


CHAPTER  VII 


THE  ROOT  — THE  FORMS  OF  ROOTS 

The  Root  System.  —  The  offices  of  the  root  are  to  hold 
the  plant  in  place,  and  to  gather  food.  Not  all  the  food 
materials,  however,  are  gathered  by  the  roots. 


'(?'.  frill  ".,,tft?V 


=*.^fe     ?>?&*    3^1, 


Fig.  32.  —  TAr-RooT 
System  of  Alfalfa. 


Fig.  33.  —  Tap-root  of  the  Dandelion. 


The  entire  mass  of  roots  of  any  plant  is  called  its  root 
system.  The  root  system  may  be  annual,  biennial  or  peren- 
nial, herbaceous  or  woody,  deep  or  shallow,  large  or  small. 

Kinds  of  Roots.  —  A  strong  leading  central  root,  which 
runs  directly  downwards,  is  a  tap-root.    The  tap-root  forms 

32 


THE   ROOT— THE   FORMS    OF  ROOTS 


33 


an  axis  from  which  the  side  roots  may  branch.  The  side 
or  spreading  roots  are  usually  smaller.  Plants  that  have 
such  a  root  system  are  said  to  be  tap-rooted.  Examples 
are  red  clover,  alfalfa,  beet,  turnip, 
radish,  burdock,  dandelion,  hickory 
(Figs.  32,  33). 

A  fibrous  root  system  is  one  that 
is  composed  of  many  nearly  equal 
slender  branches.  The  greater 
number  of  plants  have  fibrous  roots. 
Examples  are  many  common 
grasses,  wheat,  oats,  corn.  The 
buttercup  in  Fig.  34  has  a  fibrous 
root  system.  Many  trees  have  a 
strong  tap-root  when  very  young, 
but  after  a  while  it  ceases  to  ex- 
tend strongly  and  the  side  roots 
develop  until  finally  the  tap-root 
character  disappears. 

Shape  and  Extent  of  the  Root  Sys- 
tem. —  The  depth  to  which  roots 
extend  depends  on  the  kind  of  plant,  and  the  nature  of  the 
soil.  Of  most  plants  the  roots  extend  far  in  all  directions 
and  lie  comparatively  near  the  surface.  The  roots  usually 
radiate  from  a  common  point  just  beneath  the  surface  of 
the  ground. 

The  roots  grow  here  and  there  in  search  of  food,  often 
extending  much  farther  in  all  directions  than  the  spread 
of  the  top  of  the  plant.  Roots  tend  to  spread  farther  in 
poor  .soil  than  in  rich  soil,  for  the  same  size  of  plant. 
The  root  has  no  such  definite  form  as  the  stem  has.  Roots 
are  usually  very  crooked,  because  they  are  constantly 
turned  aside  by  obstacles.      Examine  roots  in  stony  soil. 


Fig.  34.  —  A  Buttercup 
Plant,  with  fibrous  roots. 


34 


PLANT  BIOLOGY 


The  extent  of  root  surface  is  usually  very  large,  for  the 
feeding  roots  arc  line  and  very  numerous.  An  ordinary 
plant  of  Indian  corn  may  have  a  total  length  of  root 
(measured  as  if  the  roots  were  placed  end  to  end)  of  several 
hundred  feet. 

The  fine  feeding  roots  are  most  abundant  in  the  richest 
part  of  tJie  soil.  They  are  attracted  by  the  food  materials. 
Roots  often  will  completely  surround  a  bone  or  other 
morsel.  When  roots  of  trees  are  exposed,  observe  that 
most  of  them  are  horizontal  and  lie  near  the  top  of  the 
ground.  Some  roots,  as  of  willows,  extend  far  in  search 
of  water.  They  often  run  into  wells  and  drains,  and  into 
the  margins  of  creeks  and  ponds.  Grow  plants  in  a  long 
narrow  box,  in  one  end  of  which  the  soil  is  kept  very  dry 
and  in  the  other  moist :  observe  where  the  roots  grow. 

Buttresses.  —  With  the  increase  i«n  diameter,  the  upper 
roots  often  protrude  above  the  ground  and  become  bracing 
buttresses.     These  buttresses  are  usually  largest  in   trees 

which  always  have  been 
exposed  to  strong  winds 
(Fig.  35).  Because  of 
growth  and  thickening, 
the  roots  elevate  part  of 
their  diameter,  and  the 
washing  away  of  the  soil 
makes  them  to  appear  as 
if  having  risen  out  of 
the  ground. 


«%iS®C 


•  The  Bracing  Base  of  a 
Field  Pine. 


Fig.  35 

Aerial  Roots.  —  Although  roots  usually  grow  underground, 
there  are  some  that  naturally  grata  above  ground.  These 
usually  occur  on  climbing  plants,  the  roots  becoming  sup- 
ports or  fulfilling  the  office  of  tendrils.  These  aerial  roots 
usually  turn  away  from  the  light,  and  therefore  enter  the 


THE  ROOT—  THE   FORMS   OF  ROOTS 


35 


crevices  and  dark  places  of  the  wall  or  tree  over  which  the 
plant    a^   climbs.     The  trumpet  creeper  (Fig.  36),  true  or 

English  ivy,  and  poison  ivy  climb  by 

means  of  roots. 


Fig.  37.  — Aerial  Roots  of  an  Orchid. 

In  some  plants  all  the  roots  are 
aerial ;  that  is,  the  plant  grows  above 
ground,  and  the  roots  gather  food 
from  the  air.  Such  plants  usually 
grow  on  trees.  They  are  known  as 
epiphytes  or  air-plants.  The  most  fa- 
miliar examples  are  some  of  the  tropi- 
cal orchids,  which  are  grown  in  glass- 
houses (Fig.  37).  Rootlike  organs  of  dodder  and  other 
parasites  are  discussed  in  a  future  chapter. 


Fig.  36. —  Aerial  Roots 
of  Trumpet  Creeper 
or  Tecoma. 


3^ 


PLANT  BIOLOGY 


Some  plants  bear  aerial  roots,  that  may  propagate  the 
plant  or  may  act  as  braces.  They  are  often  called  prop-roots. 
The  roots  of  Indian  corn  are  familiar  (Fig.  38).  Many 
ficus  trees,  as  the  banyan  of  India,  send  out  roots  from 
their  branches  ;  when  these  roots  reach  the  ground  they 
take  hold  and  become  great  trunks,  thus  spreading  the 
top  of  the  parent  tree  over  large 
areas.  The  muscadine  grape  of  the 
Southern  states  often  sends  down 
roots  from  its  stems.  The  man- 
grove tree  of  the  tropics  grows  along 
seashores  and  sends  down  roots 
from  the  overhanging  branches 
(and  from  the  fruits)  into  the  shal- 
low water,  and  thereby  gradually 
marches  into  the  sea.  The  tangled 
mass  behind  catches  the  drift,  and 
soil  is  formed. 

Adventitious  Roots.  —  Sometimes 
roots  grow  from  the  stem  or  other 
unusual  places  as  the  result  of  some 
accident  to  the  plant,  being  located 
without  known  method  or  law. 
They  are  called  adventitious  (chance) 
roots.  Cuttings  of  the  stems  of 
roses,  figs,  geraniums,  and  other  plants,  when  planted, 
send  out  adventitious  roots  and  form  new  plants.  The 
ordinary  roots,  or  soil  roots,  are  of  course  not  classed  as 
adventitious  roots.  The  adventitious  roots  arise  on  occa- 
sion, and  not  as  a  normal  or  regular  course  in  the  growth 
of  the  plant. 

No  two  roots  are  alike ;  that  is,  they  vary  among  them- 
selves as  stems  and  leaves  do.     Each  kind  of  plant  has  its 


Fig.  38.  —  Indian  Corn, 
showing  the  brace  roots 
at  00. 


THE  ROOT— THE   FORMS   OF  ROOTS 


17 


rwnform  or  habit  of  root  ( Fig.  39).  Carefully  wash  away 
the  soil  from  the  roots  of  any  two  related  plants,  as  oats 
and  wheat,  and  note  the  differences  in  size,  depth,  direc- 
tion, mode  of  branching,  num- 
ber of   fibrils,  color,   and  other 


FIG.  39.  — Roots  of  Barley  at  A  and  Corn  at  B. 
Carefully  trace  the  differences. 

features.  The  character  of  the  root  system  often  governs 
the  treatment  that  the  farmer  should  give  the  soil  in  which 
the  plant  or  crop  grows. 

Roots  differ  not  only  in  their  form  and  habit,  but  also  in 
color  of  tissue,  character  of  bark  or  rind,  and  other  features. 
It  is  excellent  practice  to  try  to  identify  different  plants  by 
means  of  their  roots.  Let  each  pupil  bring  to  school  two 
plants  with  the  roots  very  carefully  dug  up,  as  cotton, 
corn,  potato,  bean,  wheat,  rye,  timothy,  pumpkin,  clover, 
sweet  pea,  raspberry,  strawberry,  or  other  common  plants. 

Root  Systems  of  Weeds.  —  Some  weeds  are  pestiferous 
because  they  seed  abundantly,  and  others  because  their 
underground  parts  run  deep  or  far  and  are  persistent. 
Make  out  the  root  systems  in  the  six  worst  weeds  in  your 
locality. 


CHAPTER    VIII 


THE  ROOT.  —  FUNCTION  AND  STRUCTURE 


The  function  of  roots  is  twofold,  —  to  provide  support  or 
anchorage  for  the  plant,  and  to  collect  and  convey  food  ma- 
terials. The  first  function  is  considered  in  Chapter  VII; 
we  may  now  give  attention  in  more  detail  to  the  second. 

The  feeding  surface  of  the  roots 
is  near  their  ends.  As  the  roots 
become  old  and  hard,  they  serve 
only  as  channels  through  wJiicJi 
food  passes  and  as  holdfasts  or 
supports  for  the  plant.  The  root- 
hold  of  a  plant  is  very  strong. 
Slowly  pull  upwards  on  some  plant, 
and  note  how  firmly  it  is  anchored 
in  the  soil. 

Roots  have  power  to  choose  their 
food;  that  is,  they  do  not  absorb 
all  substances  with  which  they 
come  in  contact.  They  do  not  take 
up  great  quantities  of  useless  or 
harmful  materials,  even  though 
these  materials  may  be  abundant  in  the  soil  ;  but  they 
may  take  up  a  greater  quantity  of  some  of  the  plant-foods 
than  the  plant  can  use  to  advantage.  Plants  respond  very 
quickly  to  liberal  feeding,  — that  is,  to  the  application  of 
plant-food  to  the  soil  (Fig  40).  The  poorer  the  soil,  the 
more  marked  are  the  results,  as  a  rule,  of  the  application 


Fig.  40.  —  Wheat  growing 
under  Different  Soil 
Treatments.  Soil  defi- 
cient in  nitrogen ;  com- 
mercial nitrogen  applied 
to  pot  3  (on  right). 


THE  ROOT—  TL'XCTIOX  AND   STRUCTURE 


39 


of  fertilizers.  Certain  substances,  as  common  salt,  will  kill 
the  roots. 

Roots  absorb  Substances  only  in  Solution.  —  Substances 
cannot  be  taken  in  solid  particles.  These  materials  are 
in  solution  in  the  soil  water,  and  the  roots  themselves 
also  have  the  power  to  dissolve  the  soil  materials  to  some 
extent  by  means  of  substances  that 
they  excrete.  The  materials  that  ^xZ 
come  into  the  plant  through  the 
roots  are  water  and  mostly  the  min- 
eral substances,  as  compounds  of  po- 
tassium, iron,  phosphorus,  calcium, 
magnesium,  sulfur,  and  chlorine. 
These  mineral  substances  compose 
the  ash  when  the  plant  is  burned. 
The  carbon  is  derived  from  the  air 
through  the  green  parts.  Oxygen 
is  derived  from  the  air  and  the  soil 
water. 

Nitrogen  enters  through  the  Roots. 
—  All  plants  must  have  nitrogen  ; 

yet,  although   about  four  fifths  of    Fig.  41.— Nodules  on  Roots 

.,...,  ,  of  Red  Clover. 

the  air  is  nitrogen,  plants  are  not 

able,  so  far  as  we  know,  to  take  it  in  through  their  leaves. 
It  enters  through  the  roots  in  combination  with  other  ele- 
ments, chiefly  in  the  form  of  nitrates  (certain  combinations 
with  oxygen  and  a  mineral  base).  The  great  family  of 
leguminous  plants,  however  (as  peas,  beans,  cowpea, 
clover,  alfalfa,  vetch),  use  the  nitrogen  contained  in  the  air 
in  the  soil.  They  are  able  to  utilize  it  through  the  agency 
of  nodules  on  their  roots  (Figs.  41,  42).  These  nodules 
contain  bacteria,  which  appropriate  the  free  or  uncom- 
bined  nitrogen  and  pass  it  on  to  the  plant.     The  nitrogen 


40 


PLANT  BIOLOGY 


becomes  incorporated   in   the   plant  tissue,   so  that  these 
crops  are  high   in  their  nitrogen  content.     Inasmuch  as 

nitrogen  in  any  form  is 
expensive  to  purchase  in 
fertilizers,  the  use  of  legu- 
minous crops  to  plow  under 
is  a  very  important  agricul- 
tural practice  in  preparing 
the  land  for  other  crops. 
In  order  that  leguminous 
crops  may  acquire  atmos- 
pheric nitrogen  more  freely 
and  thereby  thrive  better, 
the  land  is  sometimes  sown 
or  inoculated  with  the  nod- 
ule-forming bacteria. 


Fig.  42.— Nodules  on  Vetch. 


Roots  require  moisture  in  order  to  serve  the  plant.  The 
soil  water  that  is  valu- 
able to  the  plant  is  not 
the  free  water,  but  the 
thin  film  of  moisture 
which  adheres  to  each 
little  particle  of  soil.  The 
finer  the  soil,  the  greater 
the  number  of  particles, 
and  therefore  the  greater 
is  the  quantity  of  film 
moisture  that  it  can  hold. 
This  moisture  surround- 
ing the  grains  may  not 
be  perceptible,  yet  the 
plant  can  use  it.  Root  absorption  may  continue  in  a  soil 
which  seems  to  be  dust  dry.     Soils  that  are  very  hard  and 


Fig.  43.  —  Two  Kinds  of  Sou.  that  have 
been  Wet  and  then  Dried.  The 
loamy  soil  above  remains  loose  and  capa- 
ble of  growing  plants ;  the  clay  soil  below 
has  baked  and  cracked. 


THE  ROOT— FUNCTION  AND   STRUCTURE 


41 


"baked"  (Fig.  43)  contain  very  little  moisture  or  air, — 
not  so  much  as  similar  soils  that  are  granular  or  mellow. 

Proper  Temperature  for  Root  Action.  —  The  root  must  be 
warm  in  order  to  perform  its  functions.  Should  the  soil  of 
fields  or  greenhouses  be  much  colder  than  the  air,  the 
plant  suffers.  When  in  a  warm  atmosphere,  or  in  a  dry 
atmosphere,  plants  need  to  absorb  much  water  from  the 
soil,  and  the  roots  must  be  warm  if  the  root-hairs  are  to 
supply  the  water  as  rapidly  as  it  is  needed.  If  the  roots  arc 
chilled,  the  plant  may  wilt  or  die. 

Roots  need  Air.  —  Corn  on  land  that  has  been  flooded  by 
heavy  rains  loses  its  green  color  and  turns  yellow.  Besides 
diluting  plant-food,  the  water  drives  the  air  from  the  soil,  and 
this  suffocation  of  the  roots  is  very  soon  ap- 
parent in  the  general  ill  health  of  the  plant. 
Stirring  or  tilling  the  soil  aerates  it.  Water 
plants  and  bog  plants  have  adapted  them- 
selves to  their  particular  conditions.  They 
get  their  air  either  by  special  surface  roots, 
or  from  the  water  through  stems  and  leaves. 

Rootlets.  —  Roots  divide  into  the  thinnest 
and  finest  fibrils :  there  are  roots  and  there 
are  rootlets.  The  smallest  rootlets  are  so 
slender  and  delicate  that  they  break  off 
even  when  the  plant  is  very  carefully  lifted 
from  the  soil. 

The  rootlets,  or  fine  divisions,  are  clothed  with  the  root- 
hairs  (Figs.  44,  45,  46).  These  root-hairs  attach  to  the 
soil  particles,  and  a  great  amount  of  soil  is  thus  brought 
into  actual  contact  with  the  plant.  These  are  very  deli- 
cate prolonged  surface  cells  of  the  roots.  They  are  borne 
for  a  short  distance  just  back  of  the  tip  of  the  root. 

Rootlet  and  root-hair  differ.      The  rootlet  is  a  compact 


Fig.  44.  —  Root- 
hairs  of  the 
Radish. 


\- 


PLANT  BIOLOGY 


Fig.  45.  —  Cross-section  of  Root, 

enlarged,  showing  root-hairs. 


cellular  structure.  The  root-hair  is  a  delicate  tubular 
cell  (Fig.  45),  within  which  is  contained  living  matter 
(protoplasm);  and  the  protoplasmic  lining  membrane  of  the 

wall  governs  the  entrance  of 
water  and  substances  in  solu- 
tion. Being  long  and  tube- 
like, these  root-hairs  are 
especially  adapted  for  tak- 
ing in  the  largest  quantity 
of  solutions ;  and  they  are 
the  principal  means  by  which 
plant-food  is  absorbed  from 
the  soil,  although  the  sur- 
faces of  the  rootlets  them- 
selves do  their  part.  Water 
plants  do  not  produce  an 
abundant  system  of  root-hairs,  and  such  plants  depend 
largely  on  their  rootlets. 

The  root-hairs  are  very  small,  often  invisible.  They, 
with  the  young  roots,  are  usually  broken  off  when  the 
plant  is  pulled  up.  They  are 
best  seen  when  seeds  are  germi- 
nated between  layers  of  dark 
blotting  paper  or  flannel.  On 
the  young  roots,  they  will  be 
seen  as  a  mold-like  or  gossamer- 
like covering.  Root-hairs  soon 
die :  they  do  not  grow  into  roots. 
New  ones  form  as  the  root  grows. 
Osmosis.  —  The  water  with  its 
nourishment  goes  through  the 
thin  walls  of  the  root-hairs  and  rootlets  by  the  process 
of  osmosis.     If  there  are  two  liquids  of  different  density 


Fig.  46.  —  Root-hair,  much  en- 
larged, in  contact  with  the  soil 
particles  (s) .  Air-spaces  at  a  ; 
water-films  on  the  particles,  as 
at  w. 


THE  ROOT— FUNCTION  AXD   STRUCTURE  43 

on  the  inside  and  outside  of  an  organic  (either  vegetable 
or  animal)  membrane,  the  liquids  tend  to  mix  through  the 
membrane.  The  law  of  osmosis  is  that  the  most  rapid 
flozv  is  toward  the  denser  solution.  The  protoplasmic  lin- 
ing of  the  cell  wall  is  such  a  membrane.  The  soil  water 
being  a  weaker  solution  than  the  sap  in  the  roots,  the 
flow  is  into  the  root.  A  strong  fertilizer  sometimes  causes 
a  plant  to  wither,  or  "burns  it."     Explain.' 

Structure  of  Roots.  — The  root  that  grows  from  the  lower 
end  of  the  caulicle  is  the  first  or  primary  root.  Secondary- 
roots  branch  from  the  primary  root.  Branches  of  second- 
ary roots  are  sometimes  called  tertiary  roots.  Do  the  sec- 
ondary roots  grow  from  the  cortex,  or  from  the  central 
cylinder  of  the  primary  root?  Trim  or  peel  the  cortex 
from  a  root  and  its  branches  and  determine  whether  the 
branches  still  hold  to  the  central  cylinder  of  the  main  root. 

Internal  Structure  of  Roots.  —  A  section  of  a  root  shows 
that  it  consists  of  a  central  cylinder  (see  Fig.  45)  sur- 
rounded by  a  layer.  This  layer  is  called  the  cortex.  The 
outer  layer  of  cells  in  the  cortex  is  called  the  epidermis, 
and  some  of  the  cells  of  the  epidermis  are  prolonged 
and  form  the  delicate  root-hairs.  The  cortex  resembles 
the  bark  of  the  stem  in  its  nature.  The  central  cylinder 
contains  many  tube-like  canals,  or  "  vessels  "  that  convey 
water  and  food  (Fig.  45).  Cut  a  sweet  potato  across  (also 
a  radish  and  a  turnip)  and  distinguish  the  central  cylin- 
der, cortex  and  epidermis.  Notice  the  hard  cap  on  the  tip 
of  roots.     Roots  differ  from  stems  in  having  no  real  pith. 

Microscopic  Structure  of  Roots.  — Near  the  end  of  any 
young  root  or  shoot  the  cells  are  found  to  differ  from  each 
other  more  or  less,  according  to  the  distance  from  the 
point.  This  differentiation  takes  place  in  the  region  just 
back  of  the  growing  point.     To  study  growing  points,  use 


44 


PLANT  Bioi.oay 


the  hypocotyl  of  Indian  corn  which  has  grown  about  one 
half  inch.  Make  a  longitudinal  section.  Note  these  points 
(Fig.  47):  (a)  the  tapering  root-cap  beyond  the  growing 
point ;  (&)  the  blunt  end  of  the  root  proper  and  the  rec- 
tangular shape  of  the  cells  found  there;  (c)  the  group 
of  cells  in  the  middle  of  the  first  layers  beneath  the  root- 
cap, —  this  group  is  the  growing 
point;  (d)  study  the  slight  differ- 
ences in  the  tissues  a  short  dis- 
tance back  of  the  growing  point. 
There  are  four  regions  :  the  central 
cylinder,  made  up  of  several  rows 
of  cells  in  the  center  (//);  the  en- 
dodermis,  (c)  composed  of  a  single 
layer  on  each  side  which  separates 
the  central  cylinder  from  the  bark ; 
the  cortex,  or  inner  bark,  (e)  of  sev- 
eral layers  outside  the  endodermis  ; 
and  the  epidermis,  or  outer  layer  of 
bark  on  the  outer  edges  id).  Make 
a  drawing  of  the  section.  If  a 
series  of  the  cross-sections  of  the 
hypocotyl  should  be  made  and  stud- 
ied, beginning  near  the  growing 
point  and  going  upward,  it  would 
be  found  that  these  four  tissues  become  more  distinctly 
marked,  for  at  the  tip  the  tissues  have  not  yet  assumed 
their  characteristic  form.  The  central  cylinder  contains 
the  ducts  and  vessels  which  convey  the  sap. 

The  Root-cap.  —  Note  the  form  of  the  root-cap  shown  in 
the  microscopic  section  drawn  in  Fig.  47.  Growing  cells, 
and  especially  those  which  are  forming  tissue  by  sub- 
dividing, are  very  delicate  and   are   easily  injured.     The 


Fig.  47.  —  Growing  Point 
of  Root  of  Indian  Corn. 

d,  d,  cells  which  will  form  the 
epidermis;  /,  /,  cells  that 
will  form  bark;  e,  t,  endoder- 
mis; //,  cells  which  will  form 
the  axis  cylinder;  i,  initial 
group  of  cells,  or  growing 
point  proper;  c,  root-cap. 


THE  ROOT— FUNCTION  AND   STRUCTURE 


45 


cells  forming  the  root-cap  are  older  and 
tougher  and  are  suited  for  pushing 
aside  the  soil  that  the  root  may  pene- 
trate it. 

Region  of  most  Rapid  Growth. — The 
roots  of  a  seedling  bean  may  be  marked 
at  equal  distances  by  waterproof  ink  or 
by  bits  of  black  thread  tied  moderately 
tight.  The  seedling  is  then  replanted 
and  left  undisturbed  for  two  days. 
When  it  is  dug  up,  the  region  of  most 
rapid  growth  in  the 


K£ 


Fig.  48.  —  The  Mark- 
ing of  the  Stem 
and  Root. 


.•*■ 


Fig.  49.  —  The  Result. 


root  can  be  deter- 
mined.    Give    a   reason    why  a   root 
cannot  elongate  throughout  its  length, 
—  whether  there  is  anything  to  pre- 
vent a  young  root  from  doing  so. 

In  Fig.  48  is  shown  a  germinating 
scarlet  runner  bean  with  a  short  root 
upon    which    are    marks    made    with 
waterproof   ink ;    and  the   same   root 
(Fig.  49)  is  shown  after  it  has 
grown  longer.     Which  part  of  it 
did  not  lengthen  at  all  ?    Which 
part  lengthened  slightly  ?   Where 
is  the  region  of  most  rapid  growth? 
Geotropism.  —  Roots    turn    to- 
ward the  earth,  even  if  the  seed 
is  planted  with  the  micropyle  up. 
This  phenomenon  is  called  posi- 
tive geotropism.    Stems  grow  away 
from  the  earth.     This  is  negative 
geotropism. 


46 


PLANT  BIOLOGY 


Suggestions  (Chaps.  VI]  andVIII). — 25.  Tests  for  food.  Ex- 
amine a  number  of  roots,  including  several  fleshy  roots,  for  the 
presence  of  food  material,  making  the  tests  used  on  seeds.  26. 
Study  of  root-hairs.  Carefully  germinate  radish,  turnip,  cabbage, 
or  other  seed,  so  that  no  delicate  parts  of  the  root  will  be  injured. 
For  this  purpose,  place  a  few  seeds  in  packing-moss  or  in  the  folds 
of  thick  cloth  or  of  blotting  paper,  being  careful  to  keep  them  moist 
and  warm.  In  a  few  days  the  seed  has  germinated,  and  the  root 
has  grown  an  inch  or  two  long.  Notice  that,  except  at  a  dis- 
tance of  about  a  quarter  of  an  inch  behind  the  tip,  the  root  is 
covered  with  minute  hairs  (Fig.  44).  They  are  actually  hairs; 
that  is,  root-hairs.  Touch  them  and  they  collapse,  they  are  so 
delicate.  Dip  one  of  the  plants  in  water,  and  when  removed  the 
hairs  are  not  to  be  seen.  The  water  mats  them  together  along 
the  root  and  they  are  no  longer  evident.  Root-hairs  are  usually 
destroyed  when  a  plant  is  pulled  out  of  the  soil,  be  it  done 
ever  so  carefully.  They  cling  to  the  minute  particles  of  soil 
(Fig.  46).  The  hairs  show  best  against  a  dark  background. 
27.  On  some  of  the  blotting  papers,  sprinkle  sand  ;  observe  how 
the  root-hairs  cling  to  the  grains.  Observe  how  they  are  flat- 
tened when  they  come  in  contact  with  grains  of  sand.     28.   Root 

^ hold  of  plant.     The 

I  j  r  {(' ,  /    '  pupil      should      also 

study  the  root  hold. 
Let  him  carefully  pull 
up  a  plant.  If  a  plant 
grow  alongside  a 
fence  or  other  rigid 
object,  he  may  test 
the  root  hold  by  se- 
curing a  string  to 
the  plant,  letting  the 
string  hang  over  the 
fence,  and  then  add- 
ing weights  to  the 
string.  Will  a  stake 
of  similar  size  to  the 
plant  and  extending 
no  deeper  in  the 
ground  have  such 
firm  hold  on  the  soil  ? 
What  holds  the  ball 
of  earth  in  Fig.  50? 
29.  Roots  exert  pressure.  Place  a  strong  bulb  of  hyacinth  or 
daffodil  on  firm-packed  earth  in  a  pot ;  cover  the  bulb  nearly  to 
the  top  with  loose  earth;  place  in  a  cool  cellar;  after  some  days 


Fig.  50.  — The  Grasp  of  a  Plant  on  the  Parti- 
cles of  Earth.   A  grass  plant  pulled  in  a  garden. 


THE  ROOT— FUNCTION  AND   STRUCTURE. 


4/ 


Fir,.  51.— 
Pi  \nf  grow- 
ing in  In- 
verted Pot. 


or  weeks,  note  that  the  bulb  has  been  raised  out  of  the  earth  by 
the  forming  roots.  All  roots  exert  pressure  on  the  soil  as  they  grow. 
Explain.  30.  Response  of  roots  and  stems  to  the  force  of  gravity, 
or  geotropism.  Plant  a  fast-growing  seedling  in  a 
pot  so  that  the  plumule  extends  through  the  drain 
hole  and  suspend  the  pot  with  mouth  up  {i.e.  in 
the  usual  position).  Or  use  a  pot  in  which  a  plant 
is  already  growing,  cover  with  cloth  or  wire  gauze 
to  prevent  the  soil  from  falling,  and  suspend  the 
pot  in  an  inverted  position  (Fig.  51).  Notice  the 
behavior  of  the  stem,  and  after  a  few  days  remove 
the  soil  and  observe  the  position  of  the  root.  31.  If 
a  pot  is  laid  on  one  side,  and  changed  every  two 
days  and  laid  on  its  opposite  side,  the  effect  on  the 
root  and  stem  will  be  interesting.  32.  If  a  fleshy 
root  is  planted  wrong  end  up,  what  is  the  result  ? 
Try  it  with  pieces  of  horse-radish  root.  33.  By 
planting  radishes  on  a  slowly  revolving  wheel  the 
effect  of  gravity  may  be  neutralized.  34.  Region  of 
root  most  sensitive  to  gravity.  Lay  on  its  side  a  pot  containing  a 
growing  plant.  After  it  has  grown  a  few  days,  wash  away  the  earth 
surrounding  the  roots.  Which  turned  downward  most  decidedly, 
the  tip  of  root  or  the  upper  part  ?  35.  Soil  texture.  Carefully  turn 
up  soil  in  a  rich  garden  or  field  so  that  you  have  unbroken  lumps 
as  large  as  a  hen's  egg.     Then  break  these  lumps  apart  carefully 

with  the  fingers  and 
determine  whether 
there  are  any  traces 
or  remains  of  roots 
(Fig.  52).  Are  there 
any  pores,  holes,  or 
channels  made  by 
roots?  Are  the  roots 
in  them  still  living? 
36.  Compare  an- 
other lump  from  a 
clay  bank  or  pile 
where  no  plants 
have  been  growing. 
Is  there  any  differ- 
ence in  texture?  37.  Grind  up  this  clay  lump  very  fine,  put  it  in 
a  saucer,  cover  with  water,  and  set  in  the  sun.  After  a  time  it 
will  have  the  appearance  shown  in  the  lower  saucer  in  Fig.  43. 
Compare  this  with  mellow  garden  soil.  In  which  will  plants  grow 
best,  even  if  the  plant-food  were  the  same  in  both?  Why?  38.  To 
test  the  effect  of  moisture  on  the  plant,  let  a  plant  in  a  pot  or  box  dry 


Fig.  52. 


—  Holes  in  Soil  made  by  Roots,  now 
decayed.     Somewhat  magnified. 


48  PLANT  BIOLOGY 

out  till  it  wilts  ;  then  add  water  and  note  the  rapidity  with  which 
it  recovers.  Vary  the  experiment  in  quantity  of  water  applied. 
Does  the  plant  call  for  water  sooner  when  it  stands  in  a  sunny  win- 
dow than  when  in  a  cool  shady  place?  Prove  it.  39.  Immerse 
a  potted  plant  above  the  rim  of  the  pot  in  a  pail  of  water  and  let 
it  remain  there.  What  is  the  consequence  ?  Why  ?  40.  To  test 
the  effect  of  temperature  on  roots.  Put  one  pot  in  a  dish  of  ice 
water,  and  another  in  a  dish  of  warm  water,  and  keep  them  in  a 
warm  room.  In  a  short  time  notice  how  stiff  and  vigorous  is  the 
one  whose  roots  are  warm,  whereas  the  other  may  show  signs  of 
wilting.  41.  The  process  of  osmosis.  Chip  away  the  shell  from 
the  large  end  of  an  egg  so  as  to  expose  the  uninjured  membrane 
beneath  for  an  area  about  as  large  as  a  dime.  With  sealing-wax, 
chewing-gum,  or  paste  stick  a  quill  about  three  inches  long  to 
the  smaller  end  of  the  egg.  After  the  tube  is  in  place,  run  a 
hat  pin  into  it  so  as  to  pierce  both  shell  and  membrane  ;  or  use 
a  short  glass  tube,  first  scraping  the  shell  thin  with  a  knife  and 
then  boring  through  it  with  the  tube.  Now  set  the  egg  upon  the 
mouth  of  a  pickle  jar  nearly  full  of  water,  so  that  the  large  end 
with  the  exposed  membrane  is  beneath  the  water.  After  several 
hours,  observe  the  tube  on  top  of  the  egg  to  see  whether  the  water 
has  forced  its  way  into  the  egg  and  increased  its  volume  so  that 
part  of  its  contents  are  forced  up  into  the  tube.  If  no  tube  is  at 
hand,  see  whether  the  contents  are  forced  through  the  hole  which 
has  been  made  in  the  small  end  of  the  egg.  Explain  how  the  law 
of  osmosis  is  verified  by  your  result.  If  the  eggshell  contained 
only  the  membrane,  would  water  rise  into  it?  If  there  were  no 
water  in  the  bottle,  would  the  egg-white  pass  down  into  the  bot- 
tle ?  42.  The  region  of  most  rapid  growth.  The  pupil  should 
make  marks  with  waterproof  ink  (as  Higgins'  ink  or  indelible 
marking  ink)  on  any  soft  growing  roots.  Place  seeds  of  bean, 
radish,  or  cabbage  between  layers  of  blotting  paper  or  thick  cloth. 
Keep  them  damp  and  warm.  When  stem  and  root  have  grown 
an  inch  and  a  half  long  each,  with  waterproof  ink  mark  spaces 
exactly  one  quarter  inch  apart  (Figs.  48,  49).  Keep  the  plantlets 
moist  for  a  day  or  two,  and  it  will  be  found  that  on  the  stem  some 
or  all  of  the  marks  are  more  than  one  quarter  inch  apart ;  on  the 
root  the  marks  have  not  separated.  The  root  has  grown  beyond 
the  last  mark. 

Note  to  Teacher.  —  The  microscopic  structure  of  the  root  can 
be  determined  only  by  the  use  of  the  compound  microscope ;  but 
a  good  general  conception  of  the  structure  may  be  had  by  a  care- 
ful attention  to  the  text  and  pictures  and  to  explanations  by  the 
teacher,  if  such  microscopes  are  not  to  be  had.  See  note  at  close 
of  Chapter  X. 


CHAPTER   IX 

THE   STEM  — KINDS   AND  FORMS;    PRUNING 

The  Stem  System.  —  The  stem  of  a  plant  is  the  part 
that  bears  the  buds,  leaves,  flowers ;  and  fruits.  Its  office 
is  to  hold  these  parts  up  to  the  light  and  air  ;  and  through 
its  tissues  the  various  food-materials  and  the  life-giving 
fluids  are  distributed  to  the  growing  and  working  parts. 

The  entire  mass  or  fabric  of  stems  of  any  plant  is  called 
its  stem  system.  It  comprises  the  trunk,  branches,  and 
twigs,  but  not  the  stalks  of  leaves  and  flowers  that  die  and 
fall  away.  The  stem  system  may  be  herbaceous  or  woody, 
annual,  biennial,  or  perennial  ;  and  it  may  assume  many 
sizes  and  shapes. 

Stems  are  of  Many  Forms. — The  general  way  in  which 
a  plant  grows  is  called  its  habit.  The  habit  is  the  appear- 
ance or  general  form.  Its  habit  may  be  open  or  loose, 
dense,  straight,  crooked,  compact,  straggling,  climbing, 
erect,  weak,  strong,  and  the  like.  The  roots  and  leaves 
are  the  important  functional  or  working  parts  ;  the  stem 
merely  connects  them,  and  its  form  is  exceedingly  variable. 

Kinds  of  Stems.  —  The  stem  may  be  so  short  as  to  be 
scarcely  distinguishable.  In  such  cases  the  crown  of  the 
plant  —  that  part  just  at  the  surface  of  the  ground  —  bears 
the  leaves  and  flowers  ;  but  this  crown  is  really  a  very 
short  stem.  The  dandelion,  Fig.  33,  is  an  example.  Such 
plants  are  often  said  to  be  stemless,  however,  in  order  to 
distinguish  them  from  plants  that  have  Long  or  conspic- 
E  49 


5Q 


PLANT  BIOLOGY 


ui his    stems.      These   so<alled  stemless  plants   die  to    the 

ground  every  year. 

Stems  arc  erect  when  they  grow  straight  up  (Figs.  53, 
54).     They  are  trailing  when  they  run  along  on  the  ground, 


Fig 


53.  —  Strict  Simple 
Stem  of  Mullein. 


Fig.  54.  —  Strict  Upright  Stem 
of  Narrow-leaved  Dock. 


as  melon,  wild   morning-glory  (Fig.  55).     They  are  creep- 
ing when  they  run  on  the  ground  and  take  root  at  places, 


Fig.  55. —Trailing  Stem  of  Wild  Morning  Glory  {Convolvulus  arvensis) . 

as  the  strawberry.  They  are  decumbent  when  they  lop 
over  to  the  ground.  They  are  ascending  when  they  lie 
mostly  or  in  part  on  the  ground  but  stand  more  or  less 
upright    at    their    ends ;     example,    a    tomato.      They    are 


THE   STEMS— KINDS  AMD   FORMS;    PRUNING 


51 


climbing  when  they  cling  to  other  objects 
for  support  (Figs.  36,  56). 

Trees  in  which  the  main  trunk  or  the 
"  leader "  continues  to  grow  from  its  tip 
are  said  to  be  excurrent  in  growth.  The 
branches  arc  borne  along  the  sides  of  the 
trunk,  as  in  common  pines  (Fig.  57)  and 
spruces.  Excurrent  means  running  out  or 
running  up. 

Trees  in  which  the  main  trunk  does 
not  continue  are  said  to  be  deliques- 
cent. The  branches  arise  Jrom  one 
common  point  or  from  each  other.  The 
stem  is  lost  in  the  branches.  The  apple 
tree,  plum  (Fig.  58),  maple,  elm,  oak,  China 
tree,  are  familiar  examples.     Deliquescent 

means  dissolving  or  melting  away. 

d  *  '  Fig.  56.  — A 

Each  kind  of  plant  has  its  own  peculiar     climbing  plant 

habit  or  direction   of  growth;    spruces  al-  (a twiner). 

1  1  '■  Wf 

ways  grow  to  a  single  stem  or  trunk,  pear  ^J>r.. 


mmMww 


..W'i'i. 


Fig.  57.  —  Excurrent 

1  kink.    A  pine. 


Fin.  58.  —  Deliquescent  Trunk 
of  Plum  Tree. 


5 j  PLANT  BIOLOGY 

trees  are  always  deliquescent,  morning-glories  are  always 
trailing  or  climbing,  strawberries  are  always  creeping. 
We  do  not  know  why  each  plant  has  its  own  habit,  but 
the  habit  is  in  some  way  associated  with  the  plant's  gene- 
alogy or  with  the  way  in  which  it  has  been  obliged  to  live. 

The  stem  may  be  simple  or  branched.  A  simple  stem 
usually  grows  from  the  terminal  bud,  and  side  branches 
cither  do  not  start,  or,  if  they  start,  they  soon  perish. 
Mulleins  (Fig.  53)  are  usually  simple.     So  are  palms. 

Branched  stems  may  be  of  very  different  habit  and  shape. 
Some  stem  systems  are  narrow  and  erect ;  these  are  said 
to  be  strict  (Fig.  54).  Others  are  diffuse,  open,  branchy, 
twiggy. 

Nodes  and  Internodes. — The  parts  of  the  stem  at  which 
buds  grow  are  called  nodes  or  joints  and  the  spaces  be- 
tween the  buds  are  internodes.  The  stem  at  nodes  is 
usually  enlarged,  and  the  pith  is  usually  interrupted.  The 
distance  between  the  nodes  is  influenced  by  the  vigor  of 
the  plant :   how  ? 

0 


Fig.  59. —  Rhizome  or  Rootstock. 

Stems  vs.  Roots.  —  Roots  sometimes  grow  above  ground 
(Chap.  VII);  so,  also,  stems  sometimes  grow  underground, 
and  they  are  then  known  as  subterranean  stems,  rhizomes, 
or  rootstocks  (Fig.  59). 

Stems  normally  bear  leaves  and  buds,  and  thereby  are 
they  distinguished  from  roots;  usually,  also,  they  contain 
a  pith.  The  leaves,  however,  may  be  reduced  to  mere 
scales,  and  the  buds  beneath  them  may  be  scarcely  visible. 


THE   STEMS—  A'/XDS  AND  FORMS;    PRUNING  53 

Thus  the  "eyes"  on  a  white  potato  are  cavities  with  a 
bud  or  buds  at  the  bottom  (Fig.  60).  Sweet  potatoes  have 
no  evident  "eyes"  when  first  dug  (but  they  may  develop 
adventitious  buds  before  the  next  grow- 
ing-season). The  white  potato  is  a  stem  : 
the  sweet  potato  is  probably  a  root. 
How  Stems  elongate.  —  Roots  elongate 

by  growing  near  the  tip.      Stems  elon- 

7  •  /         ./  /       Fig.      60.  —  Sprouts 

irate  bv  growing  more  or  less  tlirougn- 

&"■'"       J     <b  0>  O  ARISING  FROM  THE 

out  the  young  or  soft  part  or  "  between  buds,  or  eyes,  of  a 
joints"  (Figs.  48,  49>  But  any  part  potato  tuber. 
of  the  stem  soon  reaches  a  limit  beyond  which  it  cannot 
grow,  or  becomes  "  fixed ";  and  the  new  parts  beyond 
elongate  until  they,  too,  become  rigid.  When  a  part  of 
the  stem  once  becomes  fixed  or  hard,  it  never  increases  in 
length  :  that  is,  the  trunk  or  woody  parts  never  grow  longer 
or  higher ;  branches  do  not  become  farther  apart  or  higher 
from  the  ground. 

Stems  are  modified  in  form  by  the  particular  or  incidental 
conditions  under  which  they  grow.  The  struggle  for  light 
is  the  chief  factor  in  determining  the  shape  and  direction 
of  any  limb  (Chap.  II).  This  is  well  illustrated  in  any 
tree  or  bush  that  grows  against  a  building  or  on  the  mar- 
gin of  a  forest  (Fig.  4).  In  a  very  dense  thicket  the 
innermost  trees  shoot  up  over  the  others  or  they  perish. 
Examine  any  stem  and  endeavor  to  determine  why  it  took 
its  particular  form. 

The  stem  is  cylindrical,  the  outer  part  being  bark  and 
the  inner  part  being  wood  or  woody  tissue.  In  the  dicoty- 
ledonous plants,  the  bark  is  usually  easily  separated  from 
the  remainder  of  the  cylinder  at  some  time  of  the  year ;  in 
monocotyledonous  plants  the  bark  is  not  free.  Growth  in 
thickness  takes  place  inside  the  covering  and  not  on  the  very 


54 


PLANT  BIOLOGY 


outside  of  the  plant  cylinder.  It  is  evident,  then,  that  the 
covering  of  bark  must  expandin  order  to  allow  of  the  expan- 
sion of  the  woody  cylinder  within  it.  The  tis- 
sues, therefore,  must  be  under  constant  pressure 
or  tension.  It  has  been  determined  that  the 
pressure  within  a  growing  trunk  is  often  as 
much  as  fifty  pounds  to  the  square  inch.  The 
lower  part  of  the  limb  in  Fig.  61  shows  that 
the  outer  layers  of  bark  (which  are  long  since 
dead,  and  serve  only  as  protective  tissue)  have 
reached  the  limit  of  their  expanding  capacity 
and  have  begun  to  split.  The  pupil  will  now 
be  interested  in  the  bark  on  the  body  of  an  old 
elm  tree  (Fig.  62);  and  he  should  be  able  to 
suggest  one  reason  why  stems  remain  cylindri- 
cal, and  why  the  old  bark  becomes  marked 
with   furrows,  scales,  and  plates. 

Most  woody  plants  increase  in  diameter  by  the 
addition  of  an  annual  layer  or  "ring"  on  the 
outside  of  the  woody  cylinder, 
underneath  the  bark.  The  monocotyledo- 
nous  plants  comprise  very  few  trees  and 
shrubs  in  temperate  climates  (the  palms, 
yuccas,  and  other  tree-like  plants  are  of 
this  class),  and  they  do  not  increase 
greatly  in  diameter  and  they  rarely  branch 
to  any  extent.  Consult  the  woodpile  for 
information  as  to  the  annual  rings. 

Bark-bound  Trees.  —  If,  for  any  rea- 
son, the  bark  should  become  so  dense 
and  strong  that  the  trunk  cannot  ex- 
pand, the  tree  is  said  to  be  "bark-bound." 
is    not   rare   in   orchard   trees  that   have  been  neglected. 


Fig.  61.— 

Cracking 

of  THE 

Bark  on  an 

Elm 

Branch. 


Fig.  62.—  Piece  of 
Bark  from  an 
Old  Elm  Trunk. 

Such  condition 


THE   STEMS— KINDS  AND  FORMS;    PRUNING 


55 


When  good  tillage  is  given  to  such  trees,  they  may  not 
be  able  to  overcome  the  rigidity  of  the  old  bark,  and, 
therefore,  do  not  respond  to  the  treatment.  Sometimes 
the  thinner-barked  parts  may  outgrow  in  diameter  the 
trunk  or  the  old  branches  below  them.  The  remedy  is 
to  release  the  tension.  This  may  be  done  either  by  soften- 
ing the  bark  (by  washes  of  soap  or  lye),  or  by  separating 
it.  The  latter  is  done  by  slitting  the  bark-bound  part 
(in  spring),  thrusting  the  point  of  a  knife  through  the 
bark  to  the  wood  and  then  drawing  the  blade  down  the 
entire  length  of  the  bark- 
bound  part.  The  slit  is 
scarcely  discernible  at  first, 
but  it  opens  with  the  growth 
of  the  tree,  filling  up  with 
new  tissue  beneath.  Let  the 
pupil  consider  the  ridges 
which  he  now  and  then  finds 
on  trees,  and  determine 
whether  they  have  any  sig- 
nificance —  whether  the  tree 
has  ever  been  released  or  in- 
jured by  natural  agencies. 

The  Tissue  covers  the 
Wounds  and  "heals"  them. 
—  This  is  seen  in  Fig.  63,  in  which  a  ring  of  tissue  rolls  out 
over  the  wound.  This  ring  of  healing  tissue  forms  most 
rapidly  and  uniformly  when  the  wound  is  smooth  and  regu- 
lar. Observe  the  healing  on  broken  and  splintered  limbs ; 
also  the  difference  in  rapidity  of  healing  between  wounds 
on  strong  and  weak  limbs.  There  is  difference  in  the 
rapidity  of  the  healing  process  in  different  kinds  of  trees. 
Compare  the  apple  tree  and  the  peach.    This  tissue  may  in 


Fig.  63.  —  Proper  Cutting  of  a 
Branch.  The  wound  will  soon  be 
"  healed." 


56 


PLANT  BIOLOGY 


Fig.  64.  —  Erroneous 
Pruning. 


turn  become  bark-bound,  and  the  healing  may  stop.     On 
large  wounds  it  progresses  more  rapidly  the  first  few  years 

than  it  does  later.      This  roll  or 
ring  of  tissue  is  called  a  callus. 

The  callus  grows  from  the  liv- 
ing tissue  of  the  stem  just  about 
the  wound.  It  cannot  cover  long 
dead  stubs  or  very  rough  broken 
branches  (Fig.  64).  Therefore, 
in  pruning  the  brandies  should  be 
cut  close  to  the  trunk  and  made 
even  and  smooth  ;  all  long  stubs 
must  be  avoided.  The  seat  of 
the  wound  should  be  close  to  the 
living  part  of  the  trunk,  for  the 
stub  of  the  limb  that  is  severed 
has  no  further  power  in  itself 
of  making  healing  tissue.  The 
end  of  the  remaining  stub  is 
merely  covered  over  by  the 
callus,  and  usually  remains  a 
dead  piece  of  wood  sealed  in- 
side the  trunk  (Fig.  65).  If 
wounds  do  not  heal  over  speed- 
ily, germs  and  fungi  obtain 
foothold  in  the  dying  wood 
and  rot  sets  in.  Hollow  trees 
are  those  in  which  the  decay- 
fungi  have  progressed  into  the 
inner  wood  of  the  trunk  ;  they 
have  been  infected  (Fig.  66). 

Large  wounds   should  be  protected  with  a  covering   of 
paint,  melted  wax,  or  other  adhesive  and  lasting  material, 


Fig.  65.  — Knot  in  a  Hemlock 
Log. 


THE   STEMS— KINDS  AND  FORMS;    PRUNING 


57 


Fig.  66.  — A  Knot  Hole, 
and  the  beginning  of  a 
hollow  trunk. 


to  keep  out  the  germs  and  fungi. 
A  covering  of  sheet  iron  or  tin  may- 
keep  out  the  rain,  but  it  will  not  ex- 
clude the  germs  of  decay  ;  in  fact, 
it  may  provide  the  very  moist  con- 
ditions that  such  germs  need  for 
their  growth.  Deep  holes  in  trees 
should  be  treated  by  having  all  the 
decayed  parts  removed  down  to  the 
clean  wood,  the  surfaces  painted  or 
otherwise  sterilized,  and  the  hole 
filled  with  wax  or  cement. 
Stems  and  roots  are  living,  and 

they    should    not    be    wounded    or 

mutilated     unnecessarily.      Horses 

should   never  be   hitched   to  trees. 

Supervision    should    be    exercised 

over  persons  who    run   telephone, 

telegraph,  and  electric  light  wires, 

to    see  that    they  do   not  mutilate 

trees.  Electric  light  wires  and  trol- 
ley wires,   when   carelessly   strung 

or  improperly   insulated,    may   kill 

trees  (Fig.  67). 

^>      Suggestions.  —  Forms  of  stems. 

43.  Are  trie  trunks  of  trees  ever  per- 
fectly cylindrical?  If  not,  what  may 
cause  the  irregularities  ?  Do  trunks  often 
grow  more  on  one  side  than"  the  other? 

44.  Slit  a  rapidly  growing  limb,  in  spring, 
with  a  knife  blade,  and  watch  the  re- 
sult during  the  season.  45.  Consult  the 
woodpile,  and  observe  the  variations  in  fig.  67.  — Elm  Tree  killed 
thickness  of  the  annual  rings,  and  espe-  By  a  Direct  Current 
cially  of  the  same  ring  at  different  places  from  an  Electric 
in  the  circumference.    Cross-sections  of  Railroad  System. 


58 


PLANT  BIOLOGY 


horizontal  branches  are  interesting  in  this  connection.  46.  Note 
the  enlargement  at  the  base  of  a  branch,  and  determine  whether 
this  enlargement  or  bulge  is  larger  on  long,  horizontal  limbs  than 
on  upright  ones.  Why  does  this  bulge  develop?  Does  it  serve 
as  a  brace  to  the  limb,  and  is  it  developed  as  the  result  of  constant 
strain?  47.  Strength  of  stems.  The  pupil  should  observe  the 
fact  that  a  stem  has  wonderful  strength.  Compare  the  propor- 
tionate height,  diameter,  and  weight  of  a  grass  stem  with  those  of 
the  slenderest  tower  or  steeple.  Which  has  the  greater  strength  ? 
Which  the  greater  height?  Which  will  withstand  the  most  wind? 
Note  that  the  grass  stem  will  regain  its  position  even  if  its  top  is 
bent  to  the  ground.  Note  how  plants  are  weighted  down  after  a 
heavy  rain  and  how  they  recover  themselves.  48.  Split  a  corn- 
stalk and  observe  how  the  joints  are  tied  together  and  braced  with 
fibers.  Are  there  similar  fibers  in  stems  of  pigweed,  cotton,  sun- 
flower, hollyhock  ? 


Fig.  68.  —  Potato.     What  are  roots,  and  what  stems  ?     Has  the  plant  more  than 
one  kind  of  stem  ?  more  than  two  kinds  ?     Explain. 


CHAPTER    X 

THE   STEM  — ITS    GENERAL    STRUCTURE      V 

There  are  two  main  types  of  stem  structure  in  flowering 
plants,  the  differences  being  based  on  the  arrangement  of 
bundles  or  strands  of  tissue.  These  types  are  endogenous 
and  exogenous  (page  20).  It  will  require  patient  laboratory 
work  to  understand  what  these  types  and  structures  are. 

Endogenous,  or  Monocotyledonous  Stems.  —  Examples  of 
endogenous  stems  are  all  the  grasses,  cane-brake,  sugar- 
cane, smilax  or  green-brier, 
palms,  banana,  canna,  bam- 
boo, lilies,  yucca,  aspara-  /.' 
gus,  all  the  cereal  grains.  fl 
For  our  study,  a  cornstalk 
may  be  used  as  a  type.               M  I 

A    piece    of     cornstalk,  V 

either  green  or  dead,  should 

be    in   the    hand    of  each 

.,        ,  .,  ,    .  .  .         Fig.   69.  —  Cross-section    of   Corx- 

pupil    while   studying   this  STALK   showing  the  scattered  fibro. 

leSSOn.       Fig.     69    will    also  vascular  bundles.     Slightly  enlarged. 

be  of  use.  Is  there  a  swelling  at  the  nodes  ?  Which 
part  of  the  internode  comes  nearest  to  being  perfectly 
round  ?  There  is  a  grooved  channel  running  along  one 
side  of  the  internode  :  how  is  it  placed  with  reference  to 
the  leaf  ?  with  reference  to  the  groove  in  the  internode 
below  it  ?  What  do  you  find  in  each  groove  at  its  lower 
end?  (In  a  dried  stalk  only  traces  of  this  are  usually 
seen.)     Does  any  bud  on  a  cornstalk  besides  the   one  at 

59 


Go 


PLANT  BIOLOGY 


the  top  ever  develop  ?     Where    do  suckers    come   from  ? 
Where  does  the  ear  grow  ? 

Cut  a  cross-section  of  the  stalk  between  the  nodes  (Fig. 
69).  Does  it  have  a  distinct  bark  ?  The  interior  consists 
of  soft  "pith"  and  tough  woody  parts.  The  wood  is  found 
in  strands  or  fibers.  Which  is  more  abundant  ?  Do  the 
fibers  have  any  definite  arrangement  ?  Which  strands  are 
largest?  Smallest?  The  firm  smooth  riud { which  cannot 
properly  be  called  a  bark)  consists  of  small  wood  strands 
packed  closely  together.  Grass  stems  are  hollow  cylinders; 
and  the  cornstalk,  because  of  the  lightness  of  its  contents, 
is  also  practically  a  cylinder.  Stems  of  this  kind  are  ad- 
mirably adapted  for  providing  a  strong  support  to  leaves 
and  fruit.  This  is  in  accordance  with  the  well-known  law 
that  a  hollow  cylinder  is  much  stronger  than  a  solid 
cylinder  of  the  same  weight  of  material. 
Cut  a  thin  slice  of  the  inner  soft  part  and 
hold  it  up  to  the  light.  Can  you  make  out 
a  number  of  tiny  compartments  or  cells  ? 
These  cells  consist  of  a  tissue  called  paren- 
chyma, the  tissue  from  which  when  young  all 
the  other  tissues  arise  and  differentiate  (Paren- 
chyma =' parent  +  chyma,  or  tissue).  The 
numerous  walls  of  these  cells  may  serve  to 
brace  the  outer  wall  of  the  cylinder  ;  but  their 
chief  function  in  the  young  stalk  is  to  give 
origin  to  other  cells.  Wrhen  alive  they  are 
filled  with  cell  sap  and  protoplasm. 

Trace  the  woody  strands  through  the  nodes. 
Do  they  ascend  vertically  ?  Do  they  curve 
toward  the  rind  at  certain  places  ?  Compare 
their  course  with  the  strands  shown  in  Fig.  70.  The  woody 
strands  consist  chiefly  of  tough  fibrous  cells  that  give  rigidity 


Fig.  70.  —  Dia- 
gram toshow 
the  Course  ok 

FlBRO-VASCU- 

lar  Bundles 

IN  MoM  hi  11  V- 
LEDONS. 


THE   STEM —ITS    GEXERAI.   STRUCTURE 


6l 


Fig.  71. — Diagram  of 
Wood  Strands  or 

FlBKO- VASCULAR 

Bundles  in  a 
Root,  showing  the 
wood  (x)  and  bast 
(/)  separated. 


and  strength  to  tJic  plant,  and  of  long  tubular  interrupted 
canals  that  serve  to  convey  sap  upward  from  the  root  and  to 
convey  food  downward  from  the  leaves  to  the  stem  and  roots. 
Monocotyledons,  as  shown  by  fossils,  existed  before 
dicotyledons  appeared,  and  it  is  thought  that  the  latter 
were  developed  from  ancestors  of  the 
former.  It  will  be  interesting  to  trace 
the  relationship  in  stem  structure.  It 
will  first  be  necessary  to  learn  something 
of  the  structure  of  the  wood  strand. 

Wood  Strand  in  Monocotyledons  and 
Dicotyledons.  —  Each  wood  strand  (or 
fibro- vascular  bundle)  consists  of  two 
parts  —  the  bast  and  the  wood  proper. 
The  wood  is  on  the  side  of  the  strand 
toward  the  center  of  the  stem  and  con- 
tains large  tubular  canals  that  take  the  watery  sap  upward 
from  the  roots.     The  bast  is  on  the  side  toward  the  bark 

and  contains  fine  tubes 
through  which  diffuses 
the  dense  sap  contain- 
ing digested  food  from 
the  leaves.  In  the  root 
(Fig.  71)  the  bast  and 
the  wood  are  separate, 
so  that  there  are  tivo 
kinds  of  strands. 

In  monocotyledons, 
as  already  said,  the 
strands  (or  bundles)  are 
usually  scattered  in  the 
stem  with  no  definite  arrangement  (Figs.  72,  73).  In 
dicotyledons   the   strands,    or   bundles,  are  arranged  in  a 


Fig.  72.  —  Part  of  Cross-section  of  Root- 
stock  of  Asparagus,  showing  a  few  fibro- 
vascular  bundles.     An  endogenous  stem. 


62 


PLANT  BIOLOGY 


Fig.  74.  —  Dicotyledonous  Stem  of  One  Year  at  Left 

■with  FIVE  Bundles,  and  a  two-year  stem  at  right. 
o,  the  pith;   c,  the  wood  part;    b,  the  bast  part;    a.  one  year's  growth. 

ring.      As  the  dicotyledonous   seed  germi- 
fig.  73.  —  the     nates,   five  bundles  are  usually  formed  in 

scattered        jtg  hypocotyl  (Fig.  74);  soon  five  more  are 

Bundles  or  j 

Strands,  in         interposed 

monocotyledons  between 
at  a,  and  the  bun- 
dles in  a  circle  in  them,    and 
dicotyledons  at  b.  the     multi_ 

plication  continues,  in 
tough  plants,  until  the 
bundles  touch  (Fig.  74, 
right).  The  inner  parts 
thus  form  a  ring  of  wood 
and  the  outer  parts  form 
the  inner  bark  or  bast.  A 
new  ring  of  wood  or  bast 
is  formed  on  stems  of  di- 
cotyledons each  year  and 
the  age  of  a  cut  stem  is 

_  Fig.  75.  —  Fibro-vascular  Bundle  of 

easily  determined.  Indian  Corn,  much  magnified. 

When  CrOSS-SeCtionS    Of     A,  annular  vessel ;    A\  annular  or  spiral  vessel ; 

TV,  thick-walled   vessels;      W,  tracheids   or 

monOCOtyledoilOUS  and  dl-  woody  tissue  ;    F,  sheath  of  fibrous  tissue  sur- 

COtyledonOUS   bundles   are  rounding  the  bundle  ;     FT,  fundamental  tissue 

J  or  pith  ;   S,  sieve  tissue  :     P,  sieve  plate  ;    t , 

examined     Under     the     mi-  companion  cell  •,     /,  intercellular  space,  formed 

by  tearing  down  of  adjacent  cells  ;    IV,  wood 

croscope,  it  is  readily  seen        parenchyma. 


THE  STEM— ITS   GENERAL   STRUCTURE 


63 


why  dicotyledonous  bundles  form  rings  of  wood  and  mono- 
cotyledonous  cannot  (Figs.  75  and  76).  The  dicotyledon- 
ous bundle  (Fig.  76)  has,  running  across  it,  a  layer  of  brick- 
shaped  cells  called  cambium,  which  cells  are  a  specialized 
form  of  the  parenchyma   cells   and   retain  the  power  of 


Fig.  76. —  The  Dicotyledonous  Bundle  or  Wood  Strand.    Upper  figure 
is  of  moonseed  : 

c,  cambium  ;  d,  ducts  ;  i,  end  of  first  year's  growth  ;  2,  end  of  second  year's  growth  ;  bast 
part  at  left  and  wood  part  at  right.  Lower  figure  (from  Wettstein)  is  sunflower:  h,  wood- 
cells;  £-,  vessels;  c,  cambium;  /.fundamental  tissue  or  parenchyma;  b,  bast;  bp,  bast 
parenchyma;  s,  sieve-tubes. 

growing  and  multiplying.  The  bundles  containing  cam- 
bium are  called  open  bundles.  There  is  no  cambium  in 
monocotyledonous  bundles  (Fig.  75)  and  the  bundles  are 
called  closed  bundles.  Monocotyledonous  stems  soon  cease 
to  grozv  in  diameter.     The  stem  of  a  palm  tree  is  almost 


64 


ri.AXT   HIOI.OGY 


as  large  at  the  top  as  at  the  base.  As  dicotyledonous 
plants  grow,  the  stems  become  thicker  each  year,  for  the 
delicate  active  cambium  layer  forms  new  cells  from  early 
spring  until  midsummer  or  autumn,  adding  to  the  wood 
within  and  to  the  bark  without.  As  the  growth  in  spring 
is  very  rapid,  the  first  wood-cells  formed  are  much  larger 
than  the  last  wood-cells  formed  by  the  slow  growth  of  the 


Fig.  77.  —  White  Pine  Stem,  5  years  old.    The  outermost  layer  is  bark. 

late  season,  and  the  spring  wood  is  less  dense  and  lighter 
colored  than  the  summer  wood  ;  hence  the  time  between 
two  years'  growth  is  readily  made  out  (Figs.  77  and  78). 
Because  of  the  rapid  growth  of  the  cambium  in  spring  and 
its  consequent  soft  walls  and  fluid  contents,  the  bark  of 
trees  "peels"  readily  at  that  season. 

Medullary  Rays.  —  The  first  year's  growth  in  dicotyle- 
dons forms  a  woody  ring  which  almost  incloses  the  pith, 
and  this  is  left  as  a  small  cylinder  which  does  not  grow 


STEM— ITS   GENERAL   STRUCTURE 


65 


larger,  even  if  the  tree  should  live  a  century.  It  is  not 
quite  inclosed,  however,  for  the  narrow  layers  of  soft  cells 
separating  the  bundles  remain  be- 
tween them  (Fig.  78),  forming  ra- 
diating lines  called  medullary  rays 
or  pith  rays. 

The  Several  Plant  Cells  and  their 
Functions.  —  In  the  wood  there  are 
some  parenchyma  cells  that  are 
still  with  thin  walls,  but  have  lost 
the  power  of  di- 
vision. They  are 
now  storage  cells. 
There    are    also 


P 


s 


an 


Fig.  78.  —  Arrangement  of 
Tissues  in  Two- year - 
old  Stem  of  Moonseed. 


WOod  fibers  Which   /,  pith;  /.parenchyma.     The  fibro- 
,  vascular    bundles,    or     wood 

are      LniCK-WaiieCl  strands,  are  very  prominent,  with 

Fig.  79.  — MARKINGS      and  ri^id  (7/     Fl°".  thin  medullary  rays  between. 

^  ITT  OV'O" 

in    Cell  Walls 

of  wood  fibers.    7&),  and  serve  to  support  the  sap-canals 

sp,  spiral ;  an,  annular ;  or  wood  vessels  (or  tracheids)  that  are 
formed  by  the  absorption  of  the  end 
walls  of  upright  rows  of  cells ;  the  canals 
pass  from  the  roots  to  the  twigs  and  even 
to  ribs  of  the  leaves  and  serve  to  transport 
the  root  water.  They  are  recognized  (Fig. 
79)  by  the  peculiar  thickening  of  the  wall 
on  the  inner  surface  of  the  tubes,  occur- 
ring in  the  form  of  spirals.  Sometimes  the 
whole  wall  is  thickened  except  in  spots 
called  pits  ( g,  Fig.  76).  These  thin  spots 
(Fig.  80)  allow  the  sap  to  pass  to  other 
cells  or  to  neighboring  vessels. 


Fig.  80.  —  Pits  in 
the  Cell  Wall. 


The  cambium,  as  we  have  seen,  consists   Longitudinal  section  of 

wall  at  b,  showing 

of  cells  whose  function  is  groivth.     These       pu  borders  at  0, 0. 

F 


66 


PLANT  BIOLOGY 


cells  are  thin-walled  and  filled  with  protoplasm.     During 
the  growing   season   they   are  continually   adding   to   the 

wood  within  and  the  bark  with- 
out ;  hence  the  layer  moves  out- 
ward as  it  deposits  the  new 
woody  layer  within. 

The  bark  consists  of  inner  or 
fibrous  bark  or  new  bast  (these 
fibers  in  flax  become  linen),  the 
green  or  middle  bark  which  func- 
tions somewhat  as  the  leaves, 
and  the  corky  or  outer  bark. 
The  common  word  "  bark "  is 
seen  therefore  not  to  represent 
a  homogeneous  or  simple  struc- 
ture, but  rather  a  collection  of 
several  kinds  of  tissue,  all  sepa- 
rating from  the  wood  beneath 
by  means  of  cambium.    The  new 


Fig.  8i.  — Sieve-tubes,  s,s; 

p  shows  a  top  view  of  a  sieve-plate, 
with  a  companion  cell,  c,  at  the 
side;  o  shows  sieve-plates  in  the 
side  of  the  cell.  In  s,  s  the  proto- 
plasm is  shrunken  from  the  walls        bast   COntaillS   (i)   the   sicVC-tubcS 

byreagents'  •       (Fig.  81)   which    transport   the 

sap  containing  organic  substances,  as  sugar 
and  proteids,  from  the  leaves  to  the  parts 
needing  it  (s,  Fig.  76).  These  tubes  have 
been  formed  like  the  wood  vessels,  but 
they  have  sieve-plates  to  allow  the  dense 
organic-laden  sap  to  pass  with  sufficient 
readiness  for  purposes  of  rapid  distribu- 
tion. (2)  There  are  also  thick-walled  bast 
fibers  (Fig.  82)  in  the  bast  that  serve  for 
support.  (3)  There  is  also  some  paren- 
chyma (parent  tissue)  in  the  new  bast; 
it  is  now  in  part  a  storage  tissue.     Some- 


Fig.  82.— Thick- 
walled  Bast 
Cells. 


THE   STEM— ITS   GENERAL   STRUCTURE 


67 


Fig.  83.  —  Collen- 
CHYMA  in  Wild 
Jewel-weed  or 
Touch-me-not  (Im- 
patiens). 


Fig.  84. —Grit  Cells. 


times  the  walls  of  parenchyma  cells  in  the  cortex  thicken 
at  the  corners  and  form  brace  cells  (Fig.  83)  (collenchyma) 
for  support;  sometimes  the  whole  wall  is  thickened,  form- 
ing  grit  cells    or  stoic  cells  ( Fig. 

84 ;  examples  in 

tough    parts    of 

pear,  or  in  stone 

of  fruits).  Some 

parts    serve   for 

secretions  (milk, 

rosin,  etc.)    and 

are  called   latex 

tubes. 

The  outer  bark  of  old  shoots  consists  of  corky  cells  that 
protect  from  mechanical  injury,  and  that  contain  a  fatty  sub- 
stance (suberin)  impermeable  to  water  and  of  service  to 
keep  in  moisture.  There  is  sometimes  a  cork  cambium  (or 
phellogen)  in  the  bark  that  serves  to  extend  the  bark  and 
keep  it  from  splitting,  thus  increasing  its  power  to  protect. 
Transport  of  the  "Sap." — We  shall  soon  learn  that  the 
common  word  "  sap  "  does  not  represent  a  single  or  simple 
substance.  We  may  roughly  distinguish  two  kinds  of  more 
or  less  fluid  contents:  (1)  the  root  water,  sometimes  called 
mineral  sap,  that  is  taken  in  by  the  root,  containing  its 
freight  of  such  inorganic  substances  as  potassium,  calcium, 
iron,  and  the  rest;  this  root  water  rises,  we  have  found,  in 
the  wood  vessels,  —  that  is,  in  the  young  or  "  sapwood  "  (p. 
96);  (2)  the  elaborated  or  organized  materials  passing  back 
and  forth,  especially  from  the  leaves,  to  build  up  tissues 
in  all  parts  of  the  plant,  some  of  it  going  down  to  the  roots 
and  root-hairs ;  this  organic  material  is  transported,  as  we 
have  learned,  in  the  sieve-tubes  of  the  inner  bast,  —  that  is, 
in  the  "inner  bark."     Removing  the  bark  from  a  trunk  in 


68 


PLANT  BIOLOGY 


a  girdle  will  not  stop  the  upward  rise  of  the  root  water  so 
long  as  the  wood  remains  alive  ;  but  it  will  stop  the  passage 
of  the  elaborated  or  food-stored  materials  to  parts  below 
and  thus  starve  those  parts  ;  and  if  the  girdle  does  not 
heal  over  by  the  deposit  of  new  bark,  the  tree  will  in  time 
starve  to  death.  It  will  now  be  seen  that  the  common 
practice  of  placing  wires  or  hoops  about  trees  to  hold 
them  in  position  or  to  prevent  branches  from  falling  is 
irrational,  because  such  wires  interpose  barriers  over  which 

the  fluids  cannot  pass ;  in 
time,  as  the  trunk  increases 
in  diameter,  the  wire  girdles 
the  tree.  It  is  much  better 
to  bolt  the  parts  together  by 
rods  extending  through  the 
branches  (Fig.  85).  These 
bolts  should  fit  very  tight  in 
their  holes.     Why  ? 

Wood.  —  The  main  stem 
or  trunk,  and  sometimes 
the  larger  branches,  are  the 
sources  of  lumber  and  tim- 
ber. Different  kinds  of  wood  have  value  for  their  special 
qualities.  The  business  of  raising  wood,  for  all  purposes, 
is  known  as  forestry.  The  forest  is  to  be  considered  as  a 
crop,  and  the  crop  must  be  harvested,  as  much  as  corn  or 
rice  is  harvested.  Man  is  often  able  to  grow  a  more  pro- 
ductive forest  than  nature  does. 

Resistance  to  decay  gives  value  to  wood  used  for  shingles 
{cypress,  heart  of  yellow  pine)  and  for  fence  posts  (mul- 
berry, cedar,  post  oak,  dot's  d'arc,  mesquite). 

Hardness  and  strength  are  qualities  of  great  value  in 
building.     Live  oak  is  used  in  ships.     Red  oak,  rock  maple, 


Fig.    85. —  The    Wrong    Way    to 
brace    a    Tree.     (See   Fig.    118). 


THE   STEM— ITS    GENERAL    STRUCTURE  69 

and  yellow  pine  are  used  for  floors.  The  best  flooring  is 
sawn  with  the  straight  edges  of  the  annual  rings  upward ; 
tangential  sawn  flooring  may  splinter.  Chestnut  is  common 
in  some  parts  of  the  country,  being  used  for  ceiling  and 
inexpensive  finishing  and  furniture.  Locust  and  dot's  d'arc 
(osage  orange)  are  used  for  hubs  of  wheels ;  bois  d'arc 
makes  a  remarkably  durable  pavement  for  streets.  Ebony 
is  a  tropical  wood  used  for  flutes,  black  piano  keys,  and 
fancy  articles.  Ash  is  straight  and  elastic ;  it  is  used 
for  handles  for  light  implements.  Hickory  is  very  strong 
as  well  as  elastic,  and  is  superior  to  ash  for  handles,  spokes, 
and  other  uses  where  strength  is  wanted.  Hickory  is 
never  sawn  into  lumber,  but  is  split  or  turned.  The 
"second  growth,"  which  sprouts  from  stumps,  is  most 
useful,  as  it  splits  readily.  Fast-growing  hickory  in  rich 
land  is  most  valuable.  The  supply  of  useful  hickory  is 
being   rapidly  exhausted. 

Softness  is  often  important.  White  pine  and  sweet  gum 
because  of  their  softness  and  lightness  are  useful  in  box- 
making.  "  Georgia  "  or  southern  pine  is  harder  and  stronger 
than  white  pine ;  it  is  much  used  for  floors,  ceilings,  and 
some  kinds  of  cabinet  work.  White  pine  is  used  for 
window-sash,  doors,  and  molding,  and  cheaper  grades  for 
flooring.  Hemlock  is  the  prevailing  lumber  in  the  east  for 
the  framework  and  clapboarding  of  buildings.  Redtvood 
and  Douglas  sprtice  are  common  building  materials  on  the 
Pacific  coast.  Cypress  is  soft  and  resists  decay  and  is 
superior  to  white  pine  for  sash,  doors,  and  posts  on  the 
outside  of  houses.  Cedar  is  readily  carved  and  has  a 
unique  use  in  the  making  of  chests  for  clothes,  as  its  odor 
repels  moths  and  other  insects.  Willow  is  useful  for  bas- 
kets and  light  furniture.  Basswood  or  linden  is  used  for 
light  ceiling  and  sometimes  for  cheap  floors.      Whitezuood 


;o 


PLANT   BIOLOGY 


(incorrectly  called  poplar)  is  employed  for  wagon  bodies 
and  often  for  house  finishing.  It  often  resembles  curly 
maple. 

Beauty  of  grain  and  polish  gives  wood  value  for  furni- 
ture, pianos,  and  the  like.  Mahogany  and  white  oak  are 
most  beautiful,  although  red  oak  is  also  used.  Oak  logs 
which  are  first  quartered  and  then  sawn  radially  expose  the 
beautiful  silver  grain  (medullary  rays).     Fig.  86  shows  one 

mode  of  quartering. 
The  log  is  quartered 
on  the  lines  a,  a,  b,b  ; 
then  succeeding 
boards  are  cut  from 
each  quarter  at  i, 
2,  3,  etc.  The  nearer 
the  heart  the  better 
the  "grain  "  :  why  ? 
Ordinary  boards  are 
sawn  tangentially, 
as  c,  c.  Curly  pine, 
curly  walnut,  and 
bird's-eye  maple  are 
woods  that  owe  their 
beauty  of  grain  to  wavy  lines  or  buried  knots.  Merely  a 
stump  of  curly  walnut  is  worth  several  hundred  dollars. 
Such  wood  is  sliced  very  thin  for  veneering  and  glued 
over  other  woods  in  making  pianos  and  other  pieces.  If 
the  cause  of  wavy  grain  could  be  found  out  and  such  wood 
grown  at  will,  the  discovery  would  be  very  useful.  Maple  is 
much  used  for  furniture.  BircJi  may  be  colored  so  as  very 
closely  to  represent  mahogany,  and  it  is  useful  for  desks. 

Special  Products  of  Trees. — Cork  from  the  bark  of  the 
cork  oak  in  Spain,  latex  from  the  rubber  and  sap  from  the 


Fk;.  86.  — The  Making  of  Ordinary  Boards, 
and  One  Way  of  Making  "Quartered" 
Boards. 


THE   STEM— ITS    GENERAL   STRUCTURE  J\ 

sugar  maple  trees,  turpentine  from  pine,  tannin  from  oak 
bark,  Peruvian  bark  from  cinchona,  are  all  useful  products. 

Suggestions.  —  Parts  of  a  root  and  stein  through  which  liquids 
rise.  49.  Pull  up  a  small  plant  with  abundant  leaves,  cut  off  the 
root  so  as  to  leave  two  inches  or  more  on  the  plant  (or  cut  a  leafy 
shoot  of  squash  or  other  strong-growing  coarse  plant),  and  stand  it 
in  a  bottle  with  a  little  water  in  the  bottom  which  has  been  colored 
with  red  ink  (eosin).  After  three  hours  examine  the  root;  make 
cross-sections  at  several  places.  Has  the  water  colored  the  axis 
cylinder?  The  cortex?  What  is  your  conclusion?  Stand  some 
cut  flowers  or  a  leafy  plant  with  cut  stem  in  the  same  solution  and 
examine  as  before:  conclusion?  50.  Girdle  a  twig  of  a  rapidly 
growing  bush  (as  willow)  in  early  spring  when  growth  begins  (a) 
by  very  carefully  removing  only  the  bark,  and  (b)  by  cutting  away 
also  the  sapwood.  Under  which  condition  do  the  leaves  wilt? 
Why?  51.  Stand  twigs  of  willow  in  water ;  after  roots  have  formed 
under  the  water,  girdle  the  twig  (in  the  two  ways)  above  the  roots. 
What  happens  to  the  roots,  and  why?  52.  Observe  the  swellings 
on  trees  that  have  been  girdled  or  very  badly  injured  by  wires  or 
otherwise  :  where  are  these  swellings,  and  why?  53.  Kinds  of 
wood.  Let  each  pupil  determine  the  kind  of  wood  in  the  desk, 
the  floor,  the  door  and  window  casings,  the  doors  themselves,  the 
sash,  the  shingles,  the  fence,  and  in  the  small  implements  and 
furniture  in  the  room  ;  also  what  is  the  cheapest  and  the  most 
expensive  lumber  in  the  community.  54.  How  many  kinds  of 
wood  does  the  pupil  know,  and  what  are  their  chief  uses? 

Note  to  Teacher.  —  The  work  in  this  chapter  is  intended  to  be 
mainly  descriptive,  for  the  purpose  of  giving  the  pupil  a  rational 
conception  of  the  main  vital  processes  associated  with  the  stem, 
in  such  a  way  that  he  may  translate  it  into  his  daily  thought.  It 
is  not  intended  to  give  advice  for  the  use  of  the  compound  micro- 
scope. If  the  pupil  is  led  to  make  a  careful  study  of  the  text,  draw- 
ings, and  photographs  on  the  preceding  and  the  following  pages, 
he  will  obtain  some  of  the  benefit  of  studying  microscope  sections 
without  being  forced  to  spend  time  in  mastering  microscope 
technique.  If  the  school  is  equipped  with  compound  microscope?, 
a  teacher  is  probably  chosen  who  has  the  necessary  skill  to 
manipulate  them  and  the  knowledge  of  anatomy  and  physiology 
that  goes  naturally  with  such  work ;  and  it  would  be  useless  to 
give  instruction  in  such  work  in  a  text  of  this  kind.  The  writer  is 
of  the  opinion  that  the  introduction  of  the  compound  microscope 
into  first  courses  in  botany  has  been  productive  of  harm.  Good 
and  vital  teaching  demands  first  that  the  pupil  have  a  normal, 


72 


PLANT  BIOLOGY 


direct,  and  natural  relation  to  his  subject,  as  he  commonly  meets 
it,  that  the  obvious  and  significant  features  of  the  plant  world  be 
explained  to  him  and  be  made  a  means  of  training  him.  The 
beginning  pupil  cannot  be  expected  to  know  the  fundamental 
physiological  processes,  nor  is  it  necessary  that  these  processes 
should  be  known  in  order  to  have  a  point  of  view  and  trained 
intelligence  on  the  things  that  one  customarily  sees.  Many  a 
pupil  has  had  a  so-called  laboratory  course  in  botany  without 
having  arrived  at  any  real  conception  of  what  plants  mean,  or 
without  having  had  his  mind  opened  to  any  real  sympathetic 
touch  with  his  environment.  Even  if  one's  knowledge  be  not 
deep  or  extensive,  it  may  still  be  accurate  as  far  as  it  goes,  and 
his  outlook  on  the  subject  may  be  rational. 


Fig.  87.  —  The  Many-stemmed  Thickets  of  Mangrove  of  Southern- 
most SEACOASTS,  many  of  the  trunks  being  formed  of  aerial  roots. 


CHAPTER   XI 

LEAVES  — FORM  AND   POSITION 

Leaves  may  be  studied  from  four  points  of  view,  — with 
reference  (i)  to  their  kitids  and  sJiapes;  (2)  their  position,  or 
arrangement  on  the  plant;  (3)  their  anatomy,  or  structure ; 


Fig.  8S.  —  A  Simple  Netted-veined  Leaf. 

(4)  their  function,  or  the  work  they 
perform.  This  chapter  is  concerned 
with  the  first      *  two  categories. 


Fig.  90.  —  Compound  or  Branched  Leaf 
of  Brake  (a  common  fern). 

1% 


Fig.  89.  — A  Simple  Par- 
allel-veined Leaf. 

Kinds.  —  Leaves 
are  simple  or  un- 
branched  (Figs.  88, 
89),  and  compound  or 
branched  (Fig.  90). 


74 


PLANT  BIOLOGY 


The  method  of  compounding  or  branching  follows  the 
mode  of  veining.  The  veining,  or  venation,  is  of  two  gen- 
eral kinds :  in  some  plants  the  main  veins 
diverge,  and  there  is  a  conspicuous  net- 
work of  smaller  veins ;  such  leaves  are 
netted-veined.  They  are  characteristic  of 
the  dicotyledons.  In  other  plants  the 
main  veins  are  parallel,  or  nearly  so,  and 
there  is  no  conspicuous  network ;  these 
are  parallel-veined  leaves  (Figs.  89,  102). 
These  leaves  are  the  rule  in  monocoty- 
ledonous  plants.  The  venation  of  netted- 
veined  leaves  is  pinnate  or  feather-like 
when  the  veins  arise  from  the  side  of  a 
continuous  midrib  (Fig.  91);  palmate  or 
digitate  (hand-like)  when  the  veins  arise 
from  the  apex  of  the  petiole  (Figs.  88,  92).  If  leaves  were 
divided  between  the  main  veins,  the  former  would  be 
pinnately  and  the  latter  digitately  compound. 

It   is  customary  to  speak  of  a  leaf  as  compound  only 
when  the  parts  or  branches  are  completely  separate  blades, 


Fig.  91.  —  Com- 
plete Leaves  of 
Willow. 


Fig.  92. —  Digitate-veined  Pel- 
tate Leaf  of  Nasturtium. 


Fig.  93. 


Pinnately  Compound 
Leaf  of  Ash. 


as  when  the  division  extends  to  the  midrib  (Figs.  90,  93, 
94,  95).     The  parts  or   branches    are   known    as   leaflets. 


LEAVES— FORM  AND    POSITION 


75 


Sometimes  the  leaflets  themselves  are  compound,  and  the 
whole  leaf  is  then  said  to  be  bi-compound   or  twice-com- 


Fig.  94.  —  DlGI- 
LATKLY  COMPOl  ND 

Leaf  of  Rasp- 
berry. 


Fig.  95. —  Poison  Ivy.     Leaf  and  Fruit. 

pound  (Fig.  90).  Some  leaves  are  three-compound,  four- 
compound,  or  five-compound.  Decompound  is  a  general 
term  to  express  any  degree  of 
compounding  beyond  twice-com- 
pound. 

Leaves  that  are  not  divided  as 
far  as  to  the  midrib  are  said  to 
be: 

lobed,  if  the  openings  or  sinuses 
are  not  more  than  half  the  depth 
of  the  blade  (Fig.  96); 

cleft,  if  the  sinuses  are  deeper      FlG.  96._LobEd  leaf  of 
than  the  middle;  sugar  Maple. 


76 


I'l  4NT  BIOLOGY 


Fig.  97.  — Digitatei.v  Parted  Leaves 
of  Begonia. 


parted,  if  the  sinuses 
reach  two  thirds  or  more 
to  the  midrib  (Fig.  97); 

divided,  if  sinuses 
reach  nearly  or  quite  to 
the  midrib. 

The  parts  are  called 
lobes,  divisions,  or  seg- 
ments, rather  than  leaf- 
lets. The  leaf  may  be 
pinnately  or  digitately 
A    pinnately    parted    or 


lobed,  parted,  cleft,  or  divided. 

cleft  leaf  is  sometimes  said  to  be  pinnatifid. 

Leaves  may  have 
one  or  all  of  three 
parts  —  blade,  or 
expanded  part ;  pe- 
tiole, or  stalk ;  stip- 
ules, or  -fc^c--; ~ 
appendages  ""'--- 
at  the  base  of  the 
petiole.  A  leaf  that 
has  all  three  of  these 
parts  is  said  to  be 
complete  (Figs.  91, 
106).  The  stipules 
are  often  green  and 
leaflike  and  per- 
form the  function 
of  foliage,  as  in 
the  pea  and  Japanese  quince  (the  latter  common  in  yards). 

Leaves  and  leaflets  that  have  no  stalks  are  said  to  be 
sessile  (Figs.  98,  103),  i.e.  sitting.     Find  several  examples. 


Fig.  98.  —Oblong 


ovate  Sessile  Leaves  of 
Tea. 


LEAVES— FORM  AND   POSITION 


77 


Clasp- 
ing Leaf  of  a 
Wild  Aster. 


The  same  is  said  of  flowers  and  fruits. 
The  blade  of  a  sessile  leaf  may  partly  or 
wholly  surround  the  stem,  when  it  is  said 
to  be  clasping.  Examples  :  aster  (Fig.  99), 
corn.  In  some  cases  the  leaf  runs  down 
the  stem,  forming  a  wing ;  such  leaves  are 
said  to  be  decurrent  (Fig.  100).  When 
opposite  sessile  leaves  are  joined  by  their  fig.  99 
bases,  they  are  said  to  be  connate  (Fig.  101). 
Leaflets  may  have  one    or   all  of  these 

three  parts,  but  the  stalks  of 
leaflets  are  called  petiolules 
and  the  stipules  of  leaflets  are 
called  stipels.  The  leaf  of  the 
garden  bean  has  leaflets,  peti- 
olules, and  stipels. 

The  blade  is  usually  attached 
to  the  petiole  by  its  lozver  edge. 
In  pinnate-veined  leaves,  the  petiole  seems  to 
continue  through  the  leaf  as  a  midrib  (Fig.  91). 
In  some  plants,  however,  the  petiole  joins 
the  blade  inside  or  beyond  the  margin  (Fig.  92).  Such 
leaves  are  said  to  be  pel- 
tate or  shield-shaped.  This 
mode  of  attachment  is  par- 
ticularly common  in  float- 
ing leaves  {e.g.  the  water 
lilies).  Peltate  leaves  are 
usually  digitate-veined. 

How  to  Tell  a  Leaf. —It 
is  often  difficult  to  distin- 

guishcompound  leaves  from 

Fig.  ioi.— Two  Pairs  of  Connate 

leafy  branches,  and  leaflets  Leaves  of  Honeysuckle. 


Fig.  100.  —  De- 
current 
Leaves  of 
Mullein. 


78 


/'/  t.YT  BIOLOGY 


from  leaves.  As  a  rule  leaves  can  be  distinguished  by 
the  following  tests:  (i)  Leaves  are  temporary  structures  t 
sooner  or  later  falling.  (2)  Usually  buds  arc  borne  in  their 
axils.  (3  )  Leaves  are  usually  borne  at  joints  or 
nodes.  (4)  They  arise  on  wood  of  the  current 
j'car's  growth.  (5)  They  have  a  more  or  less 
definite  arrangement.  When  leaves  fall,  the  twig 
that  bore  them  remains;  when  leaflets  fall,  the 
main  petiole  or  stalk  that  bore  them  also  falls. 

Shapes.  —  Leaves  and  leaflets  are  infinitely 
variable  in  shape.  Names  have  been  given  to 
some  of  the  more  definite  or  regular  shapes. 
These  names  are  a  part  of  the  language  of  bot- 
any. The  names  represent  ideal  or  ~.  ^_ 
typical  shapes;  there  are  no  two  \  -.\'(, 

leaves    alike    and    very  '  •'  cZ^st, 

few  that  perfectly  con- 
form to  the  definitions. 
The  shapes  are  likened 
to  those  of  familiar  ob- 
jects or  of  geometrical 
figures.  Some  of  the 
commoner  shapes  are  as 
follows  (name  original 
examples  in  each  class): 
Linear,   several  times   longer  than  broad,  with   the    sides 

\      nearly  or  quite  parallel.     Spruces  and  most  grasses 
are  examples  (Fig.  102).     In  linear  leaves,  the  main 
veins  are  usually  parallel  to  the  midrib. 
Oblong,  twice  or  thrice  as  long  as  broad,  with   the   sides 

%  parallel  for  most  of  their  length.  Fig.  103  shows  the 
short-oblong  leaves  of  the  box,  a  plant  that  is  used 
for  permanent  edgings  in  gardens. 


\y/ 


Fig.  102.  — 
Linear- 
acuminate 
Leaf  of 
Grass. 


Fig.  103.  —  Short-oblong 
Leaves  of  Box. 


LEAVES— FORM  AND  POSITION 


79 


Elliptic  differs  from  the  oblong  in  having  the  sides  gradu- 
ally tapering  to  either  end  from  the  middle.  The 
^  European  beech  (Fig.  104)  has  elliptic 
leaves.  (This  tree  is  often  planted  in 
this  country.) 
Lanceolate,  four  to  six  times  longer  than 
broad,  widest  below   the  middle,  and 

\    tapering  to  either  end.     Some  of  the 
narrow-leaved    willows  are    examples. 
Most  of    the  willows  and  the    peach 
have  oblong-lanceolate  leaves. 
Spatulate,    a   narrow    leaf  that   is  broadest 

\      toward  the  apex.     The  top  is  usually 
rounded. 


Fig.   \  104.  — 

Elliptic  Leaf 

of  Purple 

Beech. 


Fig.  105. —  Ovate 
Serrate  Leaf  of 
Hibiscus. 


Fig.  1-36. — Leaf  of  Apple,  showing  blade,  petiole, 
and  small  narrow  stipules. 

Ovate,  shaped  somewhat  like  the  longitudinal  section  of  an 
.  egg:  about  twice  as  long  as  broad,  tapering  from  near 
Wk  the  base  to  the  apex.  This  is  one  of  the  commonest 
^^    leaf  forms  (Figs.  105,  106). 


8o 


PLANT  BIOLOGY 


Obovate,  ovate  inverted,  —  the  wide  part  towards  the  apex. 

Leaves  of  mullein  and  leaflets  of  horse-chestnut  and 
V      false  indigo  are  obovate.     This  form  is  commonest 

in  leaflets  of  digitate  leaves  :  why  ? 
Reniform,  kidney-shaped.     This  form  is  sometimes  seen  in 

#wild  plants,  particularly  in  root-leaves.     Leaves  of 
wild  ginger  are  nearly  reniform. 
Orbicular,  circular  in  general  outline.     Very  few  leaves  are 
^^    perfectly   circular,    but   there    are    many     that    are 
^^    nearer  circular  than  any  other  shape  (Fig.  107). 


Fig.  107. —  Orbicular 
Lobed  Leaves. 


Fig.  108.  —  Truncate 
Leaf  of  Tulip  Tree. 


The  shape  of  many  leaves  is  described  in  combinations 
of  these  terms  :  as  ovate-lanceolate,  lanceolate-oblong. 

The  shape  of  the  base  and  apex  of  the  leaf  or  leaflet 
is  often  characteristic.  The  base  may  be  rounded  (Fig. 
104),  tapering  (Fig.  93),  cordate  or  heart-shaped  (Fig.  105), 
truncate  or  squared  as  if  cut  off.  The  apex  may  be  blunt 
or  obtuse,  acute  or  sharp,  acuminate  or  long-pointed,  trun- 
cate (Fig.  108).     Name  examples. 

The  shape  of  the  margin  is  also  characteristic  of  each 
kind  of  leaf.  The  margin  is  entire  when  it  is  not  in- 
dented or  cut  in   any  way  (Figs.   99,    103).      When   not 


LEAVES  — FORM  A. YD   POSITION 


entire,  it  may  be  undulate  or  wavy  (Fig.  92),  serrate  or 
saw-toothed  (Fig.  105),  dentate  or  more  coarsely  notched 
(Fig.  95),  crenate  or  round-toothed,  lobed,  and  the  like. 
Give  examples. 

Leaves  often  differ  greatly  in  form  on  the  same  plant. 
Observe  the  different  shapes  of  leaves  on  the  young 
growths  of  mulberries  (Fig.  2)  and  wild  grapes;  also 
on  vigorous  squash  and  pumpkin  vines.  In  some  cases 
there  may  be  simple  and 
compound  leaves  on  the 
same  plant.  This  is 
marked  in  the  so-called 
Boston  ivy  or  ampelop- 
sis  (Fig.  109),  a  vine 
that  is  used  to  cover 
brick  and  stone  build- 
ings. Different  degrees 
of  compounding,  even 
in  the  same  leaf,  may 
often  be  found  in  honey 
locust  and  Kentucky  FlG  I09._  different  forms  of  leaves 
coffee  tree.  Remarka-  FROM  ONE  PLANT  OF  ampelopsis. 
ble  differences  in  forms  are  seen  by  comparing  seed-leaves 
with  mature  leaves  of  any  plant  (Fig.  30). 

The  Leaf  and  its  Environment. — The  form  and  shape 
of  the  leaf  often  have  direct  relation  to  the  place  in  which 
the  leaf  grozvs.  Floating  leaves  arc  usually  expanded  and 
flat,  and  the  petiole  varies  in  length  with  the  depth  of 
the  water.  Submerged  leaves  are  usually  linear  or  thread- 
like, or  are  cut  into  very  narrow  divisions:  thereby 
more  surface  is  exposed,  and  possibly  the  leaves  are  less 
injured  by  moving  water.  Compare  the  sizes  of  the  leaves 
on  the  ends  of    branches  with  those   at  the   base  of    the 


82  PLANT  BIOLOGY 

branches  or  in  the  interior  of  the  tree  top.  In  dense 
foliage  masses,  the  petioles  of  the  lowermost  or  under- 
most leaves  tend  to  elongate — to  push  the  leaf  to  the  light. 

On  the  approach  of  winter  the  leaf  usually  ceases  to 
work,  and  dies.  It  may  drop,  when  it  is  said  to  be  decidu- 
ous ;  or  it  may  remain  on  the  plant,  when  it  is  said  to  be 
persistent.  If  persistent  leaves  remain  green  during  the 
winter,  the  plant  is  said  to  be  evergreen.  Give  examples 
in  each  class.  Most  leaves  fall  by  breaking  off  at  the 
lower  end  of  the  petiole  with  a  distinct  joint  or  articula- 
tion. There  are  many  leaves,  however,  that  wither  and 
hang  on  the  plant  until  torn  off  by  the  wind;  of  such 
are  the  leaves  of  grasses,  sedges,  lilies,  orchids,  and  other 
plants  of  the  monocotyledons.  Most  leaves  of  this  char- 
acter are  parallel-veined. 

Leaves  also  die  and  fall  from  lack  of  light.  Observe  the 
yellow  and  weak  leaves  in  a  dense  tree  top  or  in  any 
thicket.  Why  do  the  lower  leaves  die  on  house  plants  ? 
Note  the  carpet  of  needles  under  the  pines.  All  ever- 
greens shed  their  leaves  after  a  time.  Counting  back  from 
the  tip  of  a  pine  or  spruce  shoot,  determine  how  many 
years  the  leaves  persist.  In  some  spruces  a  few  leaves 
may  be  found  on  branches  ten  or  more  years  old. 

Arrangement  of  Leaves.  —  Most  leaves  have  a  regular 
position  or  arrangement  on  the  stem.  This  position  or 
direction  is  determined  largely  by  exposure  to  sunlight.  In 
temperate  climates  they  usually  hang  in  such  a  way  that 
they  receive  the  greatest  amount  of  light.  One  leaf  shades 
the  other  to  the  least  possible  degree.  If  the  plant  were 
placed  in  a  new  position  with  reference  to  light,  the  leaves 
would  make  an  effort  to  turn  their  blades. 

When   leaves  are   opposite    the  pairs    usually  alternate. 
That  is,  if  one  pair  stands  north  and  south,  the  next  pair 


LEAVES— FORM  AND  POSITION 


83 


stands  east  and  west.  See  the  box-elder  shoot,  on  the 
left  in  Fig.  no.  Ojie  pair  does  not  shade  the  pat)'  beneath. 
The  leaves  are  in  four  vertical  ranks. 

TJiere  are  several  kinds  of  alternate  arrangement.  In  the 
elm  shoot,  in  Fig.  no,  the  third  bud  is  vertically  above  the 
first.  This  is  true  no 
matter  which  bud  is  taken 
as  the  starting  point. 
Draw  a  thread  around 
the  stem  until  the  two 
buds  are  joined.  Set  a 
pin  at  each  bud.  Ob- 
serve that  two  buds  are 
passed  (not  counting  the 
last)  and  that  the  thread 
makes  one  circuit  of  the 
stem.  Representing  the 
number  of  buds  by  a  de- 
nominator, and  the  num- 
ber of  circuits  by  a 
numerator,  we  have  the 
fraction  J,  which  expresses 
the  part  of  the  circle  that  lies  between  any  two  buds. 
That  is,  the  buds  are  one  half  of  360  degrees  apart,  or 
180  degrees.  Looking  endwise  at  the  stem,  the  leaves 
are  seen  to  be  2-ranked.  Note  that  in  the  apple  shoot 
(Fig.  no,  right)  the  thread  makes  two  circuits  and  five 
buds  are  passed :  two-fifths  represents  the  divergence 
between  the  buds.     The  leaves  are  5-ranked» 

Every  plant  has  its  own  arrangement  of  leaves.  For 
opposite  leaves,  see  maple,  box  elder,  ash,  lilac,  honey- 
suckle, mint,  fuchsia.  For  2-ranked  arrangement,  see 
all  grasses,   Indian    corn,   basswood,   elm.     For   3-ranked 


Fig.  iio.  —  Phyllotaxy  of  Box  Elder, 
Elm,  Apple. 


84 


PLANT  BIOLOGY 


arrangement,  see  all  sedges.  For  5-ranked  (which  is  one 
of  the  commonest),  see  apple,  cherry,  pear,  peach,  plum, 
poplar,  willow.  For  8-ranked,  see  holly,  osage  orange, 
some  willows.  More  complicated  arrangements  occur  in 
bulbs,  house  leeks,  and  other  condensed  parts.  The  buds 
or  "eyes"  on  a  potato  tuber,  which  is  an  underground  stem 
(why  ?),  show  a  spiral  arrangement  (Fig.  1 1 1 ). 
The  arrangement  of  leaves  on  the  stem  is 
known  as  phyllotaxy  (literally,  "leaf  arrange- 
ment ").  Make  out  the  phyllotaxy  on  six 
different  plants  nearest  the  schoolhouse  door. 
In  some  plants,  several  leaves  occur  at  one 
level,  being  arranged  in  a  circle  around  the 
stem.  Such  leaves  are  said  to  be  verticillate, 
or  whorled.  Leaves  arranged  in  this  way  are 
usually  narrow :  why  ? 

Although  a  definite  arrangement  of  leaves 
is  the  rule  in  most  plants,  it  is  subject  to 
modification.  On  shoots  that  receive  the 
light  only  from  one  side  or  that  grow  in  dif- 
ficult positions,  the  arrangement  may  not  be 
tato  Tuber,  definite.  Examine  shoots  that  grow  on  the 
under  side  of  dense  tree  tops  or  in  other  par- 


FtG.    III. — 

Phyllotaxy 
OF  the  Po- 


em a  fresh 
long  tuber. 


tially  lighted  positions. 


Suggestions.  —  55.  The  pupil  should  match  leaves  to  determine 
whether  any  two  are  alike.  Why  ?  Compare  leaves  from  the 
same  plant  in  size,  shape,  color,  form  of  margin,  length  of  petiole, 
venation,  texture  (as  to  thickness  or  thinness),  stage  of  maturity, 
smoothness  or  hairiness.  56.  Let  the  pupil  take  an  average 
leaf  from  each  of  the  first  ten  different  kinds  of  plants  that 
he  meets  and  compare  them  as  to  the  above  points  (in  Exer- 
cise 55),  and  also  name  the  shapes.  Determine  how  the  various 
leaves  resemble  and  differ.  57.  Describe  the  stipules  of  rose, 
apple,  fig,  willow,  violet,  pea,  or  others.  58.  In  what  part  of 
.the  world  are  parallel-veined  leaves  the  more  common  ?    59.    Do 


/.  1: .  1 1  r£S  —  /■  ORM  AXD   POSI  TW.X 


85 


you  know  of  parallel-veined  leaves  that  have  lobed  or  dentate  mar- 
gins ?  60.  What  becomes  of  dead  leaves  ?  61.  Why  is  there 
no  grass  or  other  undergrowth  under  pine  and  spruce  trees  ? 
62.  Name  several  leaves  that  are  useful  for  decorations.  Why 
are  they  useful  ?  63.  What  trees  in  your  vicinity  are  most 
esteemed  as  shade  trees  ?     What  is  the  character  of  their  foliage  ? 

64.  Why  are  the  internodes  so  long  in  water-sprouts  and  suckers  ? 

65.  How  do  foliage  characters  in  corn  or  sorghum  differ  when  the 
plants  are  grown  in  rows  or  broadcast  ?  Why  ?  66.  Why  may 
removal  of  half  the  plants  increase  the  yield  of  cotton  or  sugar- 
beets  or  lettuce  ?  67.  How  do  leaves  curl  when  they  wither  ? 
Do  different  leaves  behave  differently  in  this  respect  ?  68.  What 
kinds  of  leaves  do  you  know  to  be  eaten  by  insects  ?  By  cattle? 
By  horses  ?  What  kinds  are  used  for  human  food  ?  69.  How 
would  you  describe  the  shape  of  leaf  of  peach?  apple?  elm? 
hackberry?  maple?  sweet-gum?  corn?  wheat?  cotton?  hickory? 
cowpea?  strawberry?  chrysanthemum  ?  rose?  carnation?  70.  Are 
any  of  the  foregoing  leaves  compound?  How  do  you  describe  the 
shape  of  a  com  pound  leaf  ?  71.  How  many  sizes  of  leaves  do  you 
find  on  the  bush  or  tree  nearest  the  schoolroom  door?  72.  How- 
many  colors  or  shades?  73.  How  many  lengths  of  petioles? 
74.    Bring  in  all  the  shapes  of  leaves  that  you  can  find. 


Fig.  112.  —  Cow- 
pea.  Describe 
the  leaves.  For 
what  is  the  plant 
used? 


CHAPTER    XII 


LEAVES  — STRUCTURE   OR   ANATOMY 

Besides  the  framework,  or  system  of  veins  found  in 
blades  of  all  leaves,  there  is  a  soft  cellular  tissue  called 
mesophyll,  or  leaf  parenchyma,  and  an  epidermis  or  skin 
that  covers  the  entire  outside  part. 

Mesophyll.  —  The  mesophyll  is  not  all  alike  or  homoge- 
neous. The  upper  layer  is  composed  of  elongated  cells 
placed  perpendicular  to  the  surface  of  the  leaf.  These 
are   called  palisade   cells.      These  cells   are   usually  filled 

with  green  bod- 
ies called  chlo- 
rophyll grains. 
The  grain  con- 
tains a  great 
number  of  chlo- 
rophyll drops 
imbedded  in 
the  protoplasm. 
Below  the  pali- 
sade cells  is  the 


Fig.  113.  —  Section  of  a  Leaf,  showing  the  airspaces. 

Breathing-pore  or  stoma  at  a.     The  palisade  cells  which  chiefly 
contain  the  chlorophyll  are  at  b.     Epidermal  cells  at  c. 


spongy  parenchyma,  composed  of  cells  more  or  less  spher- 
cal  in  shape,  irregularly  arranged,  and  provided  with  many 
intercellular  air  cavities  (Fig.  113).  In  leaves  of  some 
plants  exposed  to  strong  light  there  may  be  more  than  one 
layer  of  palisade  cells,  as  in  the  India-rubber  plant  and 
oleander.  Ivy  when  grown  in  bright  light  will  develop 
two  such  layers  of  cells,  but  in  shaded  places  it  may  be 

86 


LEAVES—  STRUCTURE    OR  ANATOMY  87 

found  with  only  one.  Such  plants  as  iris  and  compass 
plant,  which  have  both  surfaces  of  the  leaf  equally  exposed 
to  sunlight,  usually  have  a  palisade  layer  beneath  each 
epidermis. 

Epidermis.  —  The  outer  or  epidermal  cells  of  leaves  do 
not  bear  chlorophyll,  but  are  usually  so  transparent  that 
the  green  mesophyll  can  be  seen  through  them.  They 
often  become  very  thick-walled,  and  are  in  most  plants 
devoid  of  all  protoplasm  except  a  thin  layer  lining  the 
walls,  the  cavities  being  filled  with  cell  sap.  This  sap  is 
sometimes  colored,  as  in  the  under  epidermis  of  begonia 
leaves.  It  is  not  common  to  find  more  than  one  layer  of 
epidermal  cells  forming  each  surface  of  a  leaf.  The  epi- 
dermis serves  to  retain  moisture  in  the  leaf  and  as  a  general 
protective  covering.  In  desert  plants  the  epidermis,  as  a 
rule,  is  very  thick  and  has  a  dense  cuticle,  thereby  pre- 
venting loss  of  water. 

There  are  various  outgrowths  of  the  epidermis.  Hairs 
are  the  chief  of  these.  They  may  be  (1)  simple,  as  on 
primula,  geranium,  naegelia ;  (2)  once  branched,  as  on  wall- 
flower;  (3)  compound,  as  on  verbascum  or  mullein;  (4) 
disk-like,  as  on  shepherdia ;  (5)  stellate,  or  star-shaped,  as 
in  certain  crucifers.  In  some  cases  the  hairs  are  glandular, 
as  in  Chinese  primrose  of  the  greenhouses  {Primula 
Sinensis)  and  certain  hairs  of  pumpkin  flowers.  The  hairs 
often  protect  the  breathing  pores,  or  stomates,  from  dust 
and  water. 

Stomates  (sometimes  called  breathing-pores)  are  small 
openings  or  pores  in  the  epidermis  of  leaves  and  soft  stems 
that  allow  the  passage  of  air  and  other  gases  and  vapors 
(stomate  or  stoma,  singular ;  stomates  or  stomata,  plural). 
They  are  placed  near  the  large  intercellular  spaces  of  the 
mesophyll,   usually  in   positions   least  affected    by   direct 


88 


PLANT  BIOLOGY 


sunlight.  Fig.  114  shows  the  structure.  There  are  two 
guard-cells  at  the  mouth  of  each  stomate,  which  may  in 
most  cases  open  or  close  the  passage  as  the  conditions 
of  the  atmosphere  may  require.     The  guard-cells  contain 


Fig.  114.  — Diagram  of  Stomate  Fig.  115.  —  Stomate    of    Iw, 

OF  Ikis  (Osterhout).  showing  compound  guard-cells. 

chlorophyll.  In  Fig.  115  is  shown  a  case  in  which  there 
are  compound  guard-cells,  that  of  ivy.  On  the  margins 
of  certain  leaves,  as  of  fuchsia,  impatiens,  cabbage,  are 
openings  known  as  water-pores. 

Stoma tes  are  very  numerous,  as  will  be  seen  from  the  num- 
bers showing  the  pores  to  each  square  inch  of  leaf  surface  : 

Lower  surface        Upper  surface 

Peony J  379°  None 

Holly 63,600  None 

Lilac 160,000  None 

Mistletoe 200  200 

Tradescantia 2.000  2,000 

Garden  Flag  (iris) 11.572  n,572 

The  arrangement  of  stomates  on  the  leaf  differs  with 

each  kind  of  plant.     Fig.  116  shows  stomates  and  also  the 

outlines  of  contiguous  epidermal  cells. 

The  function  or  work  of  the  stomates 

is  to  regulate  the  passage  of  gases  into 

and   out   of    the   plant.      The  directly 

active  organs  or  parts  are  guard-cells, 

on    either    side    the    opening.       One 
Fig.  r  16.  —  Stomates  t 

of  Geranium  Leaf.       method  of  opening  is  as  follows:    The 


LEAVES—  STRUCTURE    OR  ANATOMY 


89 


K 


thicker  walls  of  the  guard-cells  (Fig.  114)  absorb  water 
from  adjacent  cells,  these  thick  walls  buckle  or  bend  and 
part  from  each  other  at  their  middles  on  either  side  the 
opening,  causing  the  stomate  to  open,  when  the  air  gases 
may  be  taken  in  and  the  leaf  gases  may  pass  out.  When 
moisture  is  reduced  in  the  leaf  tissue,  the  guard  cells  part 
with  some  of  their  contents,  the  thick  walls  , 

straighten,  and  the  faces  of  the  two  opposite  |j| 

ones  come  together,  thus  closing  the  stomate 
and  preventing  any  water  vapor  from  pass- 
ing out.  When  a  leaf  is  actively  at  work 
making  new  organic  compounds,  the  stomates 
are  usually  open;  when  unfavorable  condi- 
tions arise,  they  arc  usually  closed.  They 
also  commonly  close  at  night,  when  growth 
(or  the  utilizing  of  the  new  materials)  is  most 
likely  to  be  active.  It  is  sometimes  safer  to 
fumigate  greenhouses  and  window  gardens 
at  night,  for  the  noxious  vapors  are  less 
likely  to  enter  the  leaf.  Dust  may  clog  or 
cover  the  stomates.  Rains  benefit  plants 
by  washing  the  leaves  as  well  as  by  provid- 
ing moisture  to  the  roots. 

Lenticels.  —  On  the  young  woody  twigs 
of  many  plants  (marked  in  osiers,  cherry, 
birch)  there  are  small  corky  spots  or  eleva- 
tions known  as  lenticels  ( Fig.  117).  They  mark  the  loca- 
tion of  some  loose  cork  cells  that  function  as  stomates, 
for  green  shoots,  as  well  as  leaves,  take  in  and  discharge 
gases;  that  is,  soft  green  twigs  function  as  leaves.  Under 
some  of  these  twig  stomates,  corky  material  may  form 
and  the  opening  is  torn  and  enlarged:  the  lenticels  are 
successors  to  the  stomates.      The   stomates  lie  in  the  epi- 


Fig.  117.  —  Len- 
ticels  on 
Young  Shoot 
of  Red  Osier 
(Cornus). 


90  PLANT  BIOLOGY 

dermis,  but  as  the  twig  ages  the  epidermis  perishes  and 
the  bark  becomes  the  external  layer.  Gases  continue  to 
pass  in  and  out  through  tlic  lenticcls,  until  the  branch  be- 
comes heavily  covered  with  thick,  corky  bark.  With  the 
growth  of  the  twig,  the  lenticel  scars  enlarge  lengthwise 
or  crosswise  or  assume  other  shapes,  often  becoming  char- 
acteristic markings. 

Fibro-vascular  Bundles.  —  We  have  studied  the  fibro- 
vascular  bundles  of  stems  (Chap.  X).  These  stem  bun- 
dles continue  into  the  leaves,  ramifying  into  the  veins, 
carrying  the  soil  water  inwards  and  bringing,  by  diffusion, 
the  elaborated  food  out  through  the  sieve-cells.  Cut 
across  a  petiole  and  notice  the  hard  spots  or  areas  in  it; 
strip  these  parts  lengthwise  of  the  petiole:  what  are  they? 

Fall  of  the  Leaf.  —  In  most  common  deciduous  plants, 
when  the  season's  work  for  the  leaf  is  ended,  the  nutritious 
matter  may  be  withdrawn,  and  a  layer  of  corky  cells  is  com- 
pleted over  the  surface  of  the  stem  where  the  leaf  is  attached. 
The  leaf  soon  falls.  It  often  falls  even  before  it  is  killed 
by  frost.  Deciduous  leaves  begin  to  show  the  surface  line 
of  articulation  in  the  early  growing  season.  This  articula- 
tion may  be  observed  at  any  time  during  the  summer.  The 
area  of  the  twig  once  covered  by  the  petioles  is  called  the 
leaf-scar  after  the  leaf  has  fallen.  In  Chap.  XV  are  shown 
a  number  of  leaf-scars.  In  the  plane  tree  (sycamore  or 
buttonwood),  the  leaf-scar  is  in  the  form  of  a  ring  surround- 
ing the  bud,  for  the  bud  is  covered  by  the  hollowed  end  of 
the  petiole ;  the  leaf  of  sumac  is  similar.  Examine  with  a 
hand  lens  leaf-scars  of  several  woody  plants.  Note  the 
number  of  bundle-scars  in  each  leaf-scar.  Sections  may 
be  cut  through  a  leaf-scar  and  examined  with  the  micro- 
scope. Note  the  character  of  cells  that  cover  the  leaf- 
scar  surface. 


LEAVES— STRUCTURE    OR   ANATOMY  Cjt 

Suggestions.  —  To  study  epidermal  hairs  :  75.  For  this  study, 
use  the  leaves  of  any  hairy  or  woolly  plant.  A  good  hand  lens  will 
reveal  the  identity  of  many  of  the  coarser  hairs.  A  dissecting  micro- 
scope will  show  them  still  better.  For  the  study  of  the  cell  structure, 
a  compound  microscope  is  necessary.  Cross-sections  may  be  made 
so  as  to  bring  hairs  on  the  edge  of  the  sections  ;  or  in  some 
cases  the  hairs  may  be  peeled  or  scraped  from  the  epidermis  and 
placed  in  water  on  a  slide.  Make  sketches  of  the  different  kinds  of 
hairs.  76.  It  is  good  practice  for  the  pupil  to  describe  leaves  in 
respect  to  their  covering  :  Are  they  smooth  on  both  surfaces  ?  Or 
hairy?  Woolly?  Thickly  or  thinly  hairy?  Hairs  long  or  short? 
Standing  straight  out  or  lying  close  to  the  surface  of  the  leaf  ? 
Simple  or  branched?  Attached  to  the  veins  or  the  plane  surface? 
Color?  Most  abundant  on  young  leaves  or  old?  77.  Place  a 
hairy  or  woolly  leaf  under  water.  Does  the  hairy  surface  appear 
silvery  ?  Why  ?  Other  questions  :  78.  Why  is  it  good  practice 
to  wash  the  leaves  of  house  plants?  79.  Describe  the  leaf-scars 
on  six  kinds  of  plants  :  size,  shape,  color,  position  with  reference 
to  the  bud,  bundle-scars.  80.  Do  you  find  leaf-scars  on  mono- 
cotyledonous  plants — -corn,  cereal  grains,  lilies,  canna,  banana, 
palm,  bamboo,  green  brier?  81.  Note  the  table  on  page  88. 
Can  you  suggest  a  reason  why  there  are  equal  numbers  of  stomates 
on  both  surfaces  of  leaves  of  tradescantia  and  flag,  and  none  on 
upper  surface  of  other  leaves?  Suppose  you  pick  a  leaf  of  lilac 
(or  some  larger  leaf),  seal  the  petiole  with  wax  and  then  rub 
the  under  surface  with  vaseline  ;  on  another  leaf  apply  the  vaseline 
to  the  upper  surface  ;  which  leaf  withers  first,  and  why?  Make  a 
similar  experiment  with  iris  or  blue  flag.  82.  Why  do  leaves  and 
shoots  of  house  plants  turn  towards  the  light?  What  happens 
when  the  plants  are  turned  around  ?  83.  Note  position  of  leaves 
of  beans,  clover,  oxalis,  alfalfa,  locust,  at  night. 


CHAPTER   XIII 
LEAVES  —  FUNCTION   OR   WORK 

We  have  discussed  (in  Chap.  VIII)  the  work  or  function 
of  roots  and  also  (in  Chap.  X)  the  function  of  stems. 
We  are  now  ready  to  complete  the  view  of  the  main  vital 
activities  of  plants  by  considering  the  function  of  the 
green  parts  (leaves  and  young  shoots). 

Sources  of  Food.  —  The  ordinary  green  plant  has  but  two 
sources  from  which  to  secure  food,  —  the  air  and  the  soil. 
When  a  plant  is  thoroughly  dried  in  an  oven,  the  water 
passes  off  ;  this  water  came  from  the  soil.  The  remaining 
part  is  called  the  dry  substance  or  dry  matter.  If  the  dry 
matter  is  burned  in  an  ordinary  fire,  only  the  ash  remains; 
this  ash  came  from  the  soil.  The  part  that  passed  off  as 
gas  in  the  burning  contained  the  elements  that  came  from 
the  air ;  it  also  contained  some  of  those  that  came  from 
the  soil  —  all  those  (as  nitrogen,  hydrogen,  chlorine)  that 
are  transformed  into  gases  by  the  heat  of  a  common  fire. 
The  part  that  comes  from  the  soil  (the  ash)  is  small  in 
amount,  being  considerably  less  than  10  per  cent  and 
sometimes  less  than  i  per  cent.  Water  is  the  most 
abundant  single  constituent  or  substance  of  plants.  In  a 
corn  plant  of  the  roasting-ear  stage,  about  80  per  cent  of 
the  substance  is  water.  A  fresh  turnip  is  over  90  per 
cent  water.  Fresh  wood  of  the  apple  tree  contains  about 
45  per  cent  of  water. 

Carbon.  —  Carbon  otters  abundantly  into  the  composition 
of  all  plants.      Note  what  happens  when  a  plant  is  burned 

92 


LEAVES—  FUNCTION  OR    WORK  93 

without  free  access  of  air,  or  smothered,  as  in  a  charcoal 
pit.  A  mass  of  charcoal  remains,  a/most  as  large  as  the 
body  of  the  plant.  Charcoal  is  almost  pure  carbon,  the  ash 
present  being  so  small  in  proportion  to  the  large  amount 
of  carbon  that  we  look  on  the  ash  as  an  impurity.  Nearly- 
half  of  the  dry  substance  of  a  tree  is  carbon.  Carbon 
goes  off  as  a  gas  when  the  plant  is  burned  in  air.  It  does 
not  go  off  alone,  but  in  combination  with  oxygen  in  the 
form  of  carbon  dioxid gas,  C02- 

The  green  plant  secures  its  carbon  from  the  air.  In 
other  words,  much  of  the  solid  matter  of  the  plant  comes 
from  one  of  the  gases  of  the  air.  By  volume,  carbon  dioxid 
forms  only  a  very  small  fraction  of  1  per  cent  of  the  air. 
It  would  be  very  disastrous  to  animal  life,  however,  if  this 
percentage  were  much  increased,  for  it  excludes  the  life- 
giving  oxygen.  Carbon  dioxid  is  often  called  "foul  gas." 
It  may  accumulate  in  old  wells,  and  an  experienced  person 
will  not  descend  into  such  wells  until  they  have  been  tested 
with  a  torch.  If  the  air  in  the  well  will  not  support  com- 
bustion,—  that  is,  if  the  torch  is  extinguished,  —  it  usually 
means  that  carbon  dioxid  has  drained  into  the  place.  The 
air  of  a  closed  schoolroom  often  contains  far  too  much  of 
this  gas,  along  with  little  solid  particles  of  waste  matters. 
Carbon  dioxid  is  often  known  as  carbonic  acid  gas. 

Appropriation  of  the  Carbon.  —  The  carbon  dioxid  of  the 
air  readily  diffuses  itself  into  the  leaves  and  other  green 
parts  of  the  plant.  The  leaf  is  delicate  in  texture,  and  when 
very  young  the  air  can  diffuse  directly  into  the  tissues. 
The  stomates,  however,  are  the  special  inlets  adapted  for 
the  admission  of  gases  into  the  leaves  and  other  green 
parts.  Through  these  stomates,  or  diffusion-pores,  the  out- 
side air  enters  into  the  air-spaces  of  the  plant,  and  is  finally 
absorbed  by  the  little  cells  containing  the  living  matter. 


94  PLANT  BIOLOGY 

Chlorophyll  ("leaf  green")  is  the  agent  that  secures 
the  energy  by  means  of  which  carbon  dioxid  is  utilized. 
This  material  is  contained  in  the  leaf  cells  in  the  form  of 
grains  (p.  86);  the  grains  themselves  are  protoplasm,  only 
the  coloring  matter  being  chlorophyll.  The  chlorophyll 
bodies  or  grains  arc  often  most  abundant  near  the  upper 
surface  of  the  leaf,  where  they  can  secure  the  greatest 
amount  of  light.  Without  this  green  coloring  matter, 
there  would  be  no  reason  for  the  large  flat  surfaces  which 
the  leaves  possess,  and  no  reason  for  the  fact  that  the 
leaves  are  borne  most  abundantly  at  the  ends  of  branches, 
where  the  light  is  most  available.  Plants  with  colored 
leaves,  as  coleus,  have  chlorophyll,  but  it  is  masked  by 
other  coloring  matter.  This  other  coloring  matter  is 
usually  soluble  in  hot  water :  boil  a  coleus  leaf  and  notice 
that  it  becomes  green  and  the  water  becomes  colored. 

Plants  grown  in  darkness  are  yellow  and  slender,  and 
do  not  reach  maturity.  Compare  the  potato  sprouts  that 
have  grown  from  a  tuber  lying  in  the  dark  cellar  with 
those  that  have  grown  normally  in  the  bright  light. 
The  shoots  have  become  slender  and  are  devoid  of  chloro- 
phyll;  and  when  the  food  that  is  stored  in  the  tuber  is 
exhausted,  these  shoots  will  have  lived  useless  lives.  A 
plant  that  has  been  grown  in  darkness  from  the  seed  will 
soon  die,  although  for  a  time  the  little  seedling  will  grow 
very  tall  and  slender:  why?  Light  favors  the  production 
of  chlorophyll,  and  the  chlorophyll  is  the  agent  in  the  mak- 
ing of  the  organic  carbon  compounds.  Sometimes  chloro- 
phyll is  found  in  buds  and  seeds,  but  in  most  cases  these 
places  are  not  perfectly  dark.  Notice  how  potato  tubers  de- 
velop chlorophyll,  or  become  green,  when  exposed  to  light. 

Photosynthesis.  —  Carbon  dioxid  diffuses  into  the  leaf ; 
during  sunlight  it  is  used,  and  oxygen  is  given  off.    How  the 


LEAVES— FUNCTIOX  OR   WORK  95 

carbon  dioxid  which  is  thus  absorbed  may  be  used  in  mak- 
ing an  organic  food  is  a  complex  question,  and  need  not 
be  studied  here;  but  it  may  be  stated  that  carbon  dioxid 
and  water  are  the  constituents.  Complex  compounds  are 
built  up  out  of  simpler  ones. 

Chlorophyll  absorbs  certain  light  rays,  and  the  energy 
tints  directly  or  indirectly  obtained  is  used  by  the  living 
matter  in  uniting  the  carbon  dioxid  absorbed  from  the  air 
with  some  of  the  water  brought  up  from  the  roots.  The 
ultimate  result  usually  is  starch.  The  process  is  obscure, 
but  sugar  is  generally  one  step ;  and  our  first  definite 
knowledge  of  the  product  begins  when  starch  is  deposited 
in  the  leaves.  The  process  of  using  the  carbon  dioxid  of 
the  air  has  been  known  as  carbon  assimilation,  but  the 
term  now  most  used  is  photosynthesis  (from  two  Greek 
words,  meaning  light  and  to  put  together). 

Starch  and  Sugar. — All  starch  is  composed  of  carbon, 
hydrogen,  and  oxygen  (C6H10O5)„.  The  sugars  and  the 
substance  of  cell  walls  are  very  similar  to  it  in  composition. 
All  these  substances  are  called  carbohydrates.  In  making 
fruit  sugar  from  the  carbon  and  oxygen  of  carbon  dioxid 
and  from  the  hydrogen  and  oxygen  of  the  water,  there 
is  a  surplus  of  oxygen  (6  parts  C02  +  6  parts  H20 
=  C6H1206  +  6  Oa).  It  is  this  oxygen  that  is  given  off 
into  the  air  during  sunlight. 

Digestion.  —  Starch  is  in  the  form  of  insoluble  granules. 
When  such  food  material  is  carried  from  one  part  of  the 
plant  to  another  for  purposes  of  growth  or  storage,  it  is 
made  soluble  before  it  can  be  transported.  When  this 
starchy  material  is  transferred  from  place  to  place,  it  is 
usually  changed  into  sugar  by  the  action  of  a  diastase. 
This  is  a  process  <?/ digestion.  It  is  much  like  the  change 
of  starchy  foodstuffs  to  sugary  foods  by  the  saliva. 


96 


PLANT  BIOLOGY 


Distribution  of  the  Digested  Food.  —  After  being  changed 
to  the  soluble  form,  this  material  is  ready  to  be  used  in 
growth,  either  in  the  leaf,  in  the  stem,  or  in  the  roots. 
With  other  more  complex  products  it  is  then  distributed 

throughout  all  of  the  groiving  parts 
of  the  plant;  and  when  passing 
down  to  the  root,  it  seems  to  pass 
more  readily  through  the  inner 
bark,  in  plants  which  have  a  defi- 
nite bark.  This  gradual  down- 
ward diffusion  through  the  inner 
bark  of  materials  suitable  for 
growth  is  the  process  referred  to 
when  the  "  descent  of  sap  "  is  men- 
tioned. Starch  and  other  products 
are  often  stored  in  one  groiving 
season  to  be  7ised  in  the  next  sea- 
son. If  a  tree  is  constricted  or 
strangled  by  a  wire  around  its 
trunk  (Fig.  118),  the  digested  food 
cannot  readily  pass  down  and  it  is  stored  above  the  girdle, 
causing  an  enlargement. 

Assimilation.  —  The  food  from  the  air  and  that  from  the 
soil  unite  in  the  living  tissues.  The  "sap"  that  passes 
upwards  from  the  roots  in  the  growing  season  is  made  up 
largely  of  the  soil  water  and  the  salts  which  have  been 
absorbed  in  the  diluted  solutions  (p.  67).  This  upward- 
moving  water  is  conducted  largely  through  certain  tubular 
canals  of  the  young  zvood.  These  cells  are  never  continu- 
ous tubes  from  root  to  leaf;  but  the  water  passes  readily 
from  one  cell  or  canal  to  another  in  its  upward  course. 

The  upward-moving  water  gradually  passes  to  the  grow- 
ing parts,  and  everywhere  in    the  living  tissues,  it  is  of 


Fig.  118.  — Trunk  Girdled 
by  a  Wire.    See  Fig.  8c;. 


LEAVES  —  FUNCTION   OR   WORK  97 

course  in  the  most  intimate  contact  with  the  soluble  carbo- 
hydrates and  products  of  photosynthesis.  In  the  build- 
ing up  or  reconstructive  and  other  processes  it  is  therefore 
available.  We  may  properly  conceive  of  certain  of  the 
simpler  organic  molecules  as  passing  through  a  series  of 
changes,  gradually  increasing  in  complexity.  There  will 
be  formed  substances  containing  nitrogen  in  addition  to 
carbon,  hydrogen,  and  oxygen.  Others  will  contain  also 
sulfur  and  phosphorus,  and  the  various  processes  may 
be  thought  of  as  culminating  in  protoplasm.  Protoplasm 
is  the  living  matter  in  plants.  It  is  in  the  cells,  and  is 
usually  semifluid.  Starch  is  not  living  matter.  The 
complex  process  of  building  up  the  protoplasm  is  called 
assimilation. 

Respiration.  —  Plants  need  oxygen  for  respiration,  as 
animals  do.  We  have  seen  that  plants  need  the  carbon 
dioxid  of  the  air.  To  most  plants  the  nitrogen  of  the  air 
is  inert,  and  serves  only  to  dilute  the  other  elements ;  but 
the  oxygen  is  necessary  for  all  life.  We  know  that  all 
animals  need  this  oxygen  in  order  to  breathe  or  respire. 
In  fact,  they  have  become  accustomed  to  it  in  just  the 
proportions  found  in  the  air ;  and  this  is  now  best  for 
them.  When  animals  breathe  the  air  once,  they  make  it 
foul,  because  they  use  some  of  the  oxygen  and  give  off 
carbon  dioxid.  Likewise,  all  living  parts  of  the  plant  must 
have  a  constant  supply  of  oxygen.  Roots  also  need  it,  for 
they  respire.  Air  goes  in  and  out  of  the  soil  by  diffusion, 
and  as  the  soil  is  heated  and  cooled,  causing  the  air  to 
expand  and  contract. 

The  oxygen  passes  into  the  air-spaces  and  is  absorbed 
by  the  moist  cell  membranes.  In  the  living  cells  it  makes 
possible  the  formation  of  simpler  compounds  by  which 
energy  is  released.       This   energy    enables    the    plant    to 


98  PLANT  BIOLOGY 

work  and  grow,  and  the  final  products  of  this  action  are 
carbon  dioxid  and  water.  As  a  result  of  the  use  of  this 
oxygen  by  night  and  by  day,  plants  give  off  carbon  dioxid. 
Plants  respire  ;  but  since  they  are  stationary,  and  more  or 
less  inactive,  they  do  not  need  as  much  oxygen  as  animals, 
and  tiny  do  not  give  off  so  much  carbon  dioxid.  A  few  plants 
in  a  sleeping  room  need  not  disturb  one  more  than  a  family 
of  mice.  It  should  be  noted,  however,  that  germinating 
seeds  respire  vigorously,  hence  they  consume  much  oxy- 
gen ;  and  opening  buds  and  flowers  are  likewise  active. 

Transpiration.  —  Much  more  water  is  absorbed  by  the 
roots  than  is  used  in  growth,  and  this  surplus  water  passes 
from  the  leaves  into  the  atmosphere  by  an  evaporation  process 
known  as  transpiration.  Transpiration  takes  place  more 
abundantly  from  the  under  surfaces  of  leaves,  and  through 
the  pores  or  stomates.  A  sunflower  plant  of  the  height 
of  a  man,  during  an  active  period  of  growth,  gives  off  a 
quart  of  water  per  day.  A  large  oak  tree  may  transpire 
1 50  gallons  per  day  during  the  summer.  For  every  ounce 
of  dry  matter  produced,  it  is  estimated  that  15  to  25  pounds 
of  water  usually  passes  through  the  plant. 

When  the  roots  fail  to  supply  to  the  plant  sufficient  water 
to  equalize  that  transpired  by  the  leaves,  the  plant  wilts. 
Transpiration  from  the  leaves  and  delicate  shoots  is  in- 
creased by  all  of  the  conditions  which  increase  evapora- 
tion, such  as  higher  temperature,  dry  air,  or  wind.  The 
stomata  open  and  close,  tending  to  regulate  transpiration 
as  the  varying  conditions  of  the  atmosphere  affect  the 
moisture  content  of  the  plant.  However,  in  periods  of 
drought  or  of  very  hot  weather,  and  especially  during  a 
hot  wind,  the  closing  of  these  stomates  cannot  sufficiently 
prevent  evaporation.  The  roots  may  be  very  active  and 
yet  fail  to  absorb  sufficient  moisture  to  equalize  that  given 


LEAVES  — FUNCTION  OR    WORK  99 

off  by  the  leaves.  The  plant  shows  the  effect  (how?). 
On  a  hot  dry  day,  note  how  the  leaves  of  corn  "  roll "  tow- 
ards afternoon.  Note  how  fresh  and  vigorous  the  same 
leaves  appear  early  the  following  morning.  Any  injury  to 
the  roots,  such  as  a  bruise,  or  exposure  to  heat,  drought,  or 
cold  may  cause  the  plant  to  wilt. 

Water  is  forced  up  by  root  pressure  or  sap  pressure. 
(Exercise  99.)  Some  of  the  dew  on  the  grass  in  the  morn- 
ing may  be  the  water  forced  up  by  the  roots ;  some  of  it  is 
the  condensed  vapor  of  the  air. 

The  wilting  of  a  plant  is  due  to  the  loss  of  water  from 
the  cells.  The  cell  walls  are  soft,  and  collapse.  A  toy 
balloon  will  not  stand  alone  until  it  is  inflated  with  air 
or  liquid.  In  the  woody  parts  of  the  plant  the  cell  walls 
may  be  stiff  enough  to  support  themselves,  even  though 
the  cell  is  empty.  Measure  the  contraction  due  to  wilt- 
ing and  drying  by  tracing  a  fresh  leaf  on  page  of  note- 
book, and  then  tracing  the  same  leaf  after  it  has  been 
dried  between  papers.  The  softer  the  leaf,  the  greater 
will  be  the  contraction. 

Storage.  —  We  have  said  that  starch  may  be  stored  in 
twigs  to  be  used  the  following  year.  The  very  early  flowers 
on  fruit  trees,  especially  those  that  come  before  the  leaves, 
and  those  that  come  from  bulbs,  as  crocuses  and  tulips, 
are  supported  by  the  starch  or  other  food  that  was  organ- 
ized the  year  before.  Some  plants  have  very  special  stor- 
age reservoirs,  as  the  potato,  in  this  case  being  a  thickened 
stem  although  growing  underground.  (Why  a  thickened 
stem?  p.  84.)  It  is  well  to  make  the  starch  test  on  winter 
twigs  and  on  all  kinds  of  thickened  parts,  as  tubers  and  bulbs. 

Carnivorous  Plants.  —  Certain  plants  capture  insects  and 
other  very  small  animals  and  utilize  them  to  some  extent 
as  food.     Such  are  the  sundew,  that    has  on   the  leaves 


IOO 


ri.Axr  BIOLOGY 


sticky  hairs  that  close  over  the  insect ;  the  Venus's  flytrap 
of  the  Southern  states,  in  which  the  halves  of  the  leaves 

close  over  the  prey  like  the  jaws 
of  a  steel  trap ;  and  the  various 
kinds  of  pitcher  plants  that  col- 
lect insects  and  other  organic 
matter  in  deep,  water-filled,  flask- 
like leaf  pouches  (Fig.  1 19). 

The  sundew  and  Venus's  fly- 
trap are  sensitive  to  contact. 
Other  plants  are  sensitive  to  the 
touch  without  being  insectivo- 
rous. The  common  cultivated 
sensitive  plant  is  an  example. 
This  is  readily  grown  from  seeds 
(sold  by  seedsmen)  in  a  warm 
place.  Related  wild  plants  in 
the  south  are  sensitive.  The 
utility  of  this  sensitiveness  is  not  understood. 

Parts  that  Simulate  Leaves.  —  We  have  learned  that 
leaves  are  endlessly  modified  to  suit  the  conditions  in  which 
the  plant  is  placed.  The  most  marked  modifications  are  in 
adaptation  to  light.  On  the  other  hand,  other  organs  often 
perform  the  functions  of  leaves.  Green  shoots  function  as 
leaves.  These  shoots  may  look  like  leaves,  in  which  case 
they  are  called  cladophylla.  The  foliage  of  common 
asparagus  is  made  up  of  fine  branches :  the  real  morpho- 
logical leaves  are  the  minute  dry  functionless  scales  at  the 
bases  of  these  branchlets.  (What  reason  is  there  for  calling 
them  leaves?)  The  broad  "  leaves"  of  the  florist's  smilax 
are  cladophylla  :  where  are  the  leaves  on  this  plant?  In 
most  of  the  cacti,  the  entire  plant  body  performs  the  func- 
tions of  leaves  until  the  parts  become  cork-bound. 


Fig.  119. —  The  Common 
PITCHER  PLANT  {Sarracenia 
purpurea)  of  the  North,  show- 
ing the  tubular  leaves  and  the 
odd,  long-stalked  flowers. 


LEAVES—  FUNCTION   OR    WORK 


101 


Leaves  are  sometimes  modified  to  perform  other  functions 
than  the  vital  processes :  they  may  be  tendrils,  as  the 
terminal  leaflets  of  pea  and  sweet  pea;  or  spines,  as  in 
barberry.  Not  all  spines  and  thorns,  however,  represent 
modified  leaves:  some  of  them  (as  of  hawthorns,  osage 
orange,  honey  locust)  are  branches. 

Suggestions.  —  To  test  for  chlorophyll.  84.  Purchase  about  a 
gill  of  wood  alcohol.  Secure  a  leaf  of  geranium,  clover,  or  other 
plant  that  has  been  exposed  to  sunlight  for  a  few  hours,  and,  after 
dipping  it  for  a  minute  in  boiling  water,  put  it  in  a  white  cup  with 
sufficient  alcohol  to  cover.  Place  the  cup  in  a  shallow  pan  of 
hot  water  on  the  stove  where  it  is  not  hot  enough  for  the  alcohol 
to  take  fire.  After  a  time  the  chlorophyll  is  dissolved  by  the 
alcohol,  which  has  become  an  intense  green.  Save  this  leaf  for 
•  the  starch  experiment  (Exercise  85).  Without  chlorophyll,  the 
plant  cannot  appropriate  the  carbon  dioxid  of  the  air.  Starch 
and  photosynthesis.  85.  Starch  is  present  in  the  green  leaves 
which  have  been  exposed  to  sunlight ;  but  in  the  dark  no  starch 
can  be  formed  from  carbon  dioxid.  Apply  iodine  to  the  leaf  from 
which  the  chlorophyll  was  dissolved  in  the  previous  experiment. 
Note  that  the  leaf  is  colored  purplish  brown  throughout.  The  leaf 
contains  starch.  86.  Se- 
cure a  leaf  from  a  plant 
which  has  been  in  the  dark- 
ness for  about  two  days. 
Dissolve  the  chlorophyll  as 
before,  and  attempt  to  stain 
this  leaf  with  iodine.  No 
purplish  brown  color  is  pro- 
duced. This  shows  that 
the  starch  manufactured  in 
the  leaf  may  be  entirely 
removed  during  darkness. 
87.  Secure  a  plant  which 
has  been  kept  in  darkness 
for  twenty- four  hours  or 
more.  Split  a  small  cork 
and  pin  the  two  halves  on  opposite  sides  of  one  of  the  leaves,  as 
shown  in  Fig.  120.  Place  the  plant  in  the  sunlight  again.  After 
a  morning  of  bright  sunshine  dissolve  the  chlorophyll  in  this  leaf 
with  alcohol  ;  then  stain  the  leaf  with  the  iodine.  Notice  that  the 
leaf  is  stained  deeply  except  where  the  cork  was  ;  there  sunlight  and 
carbon  dioxid  were  excluded,  Fig.  121.     There  is  no  starch  in  the 


Fig.  120.  —  Exclud- 
ing Light  and 
C02  from  Part 
of  a  Leaf. 


Fig.  121.  —  The 
Result. 


102 


J '/A  XT  BIOLOGY 


it  may  be 
to  be  again 
the     living 


covered  area.  88.  Plants  or  parts  of  plants  that  have  developed 
no  chlorophyll  can  form  no  starch.  Secure  a  variegated  leaf  of 
coleus,  ribbon  grass,  geranium,  or  of  any  plant  showing  both  white 
and  green  areas.  On  a  day  of  bright  sunshine,  test  one  of  these 
leaves  by  the  alcohol  and  iodine  method  for  the  presence  of  starch. 
Observe  that  the  parts  devoid  of  green  color  have  formed  no 
starch.  However,  after  starch  has  once  been  formed  in  the  leaves, 
changed  into  soluble  substances  and  removed, 
converted  into  starch  in  certain  other  parts  of 
tissues.  To  test  the  giving  off  of  oxygen  by  day. 
89.  Make  the  experiment  illus- 
trated in  Fig.  122.  Under  a  fun- 
nel in  a  deep  glass  jar  containing 
fresh  spring  or  stream  water  place 
fresh  pieces  of  the  common 
waterweed  elodea  (or  anacharis). 
Have  the  funnel  considerably 
smaller  than  the  vessel,  and  sup- 
port the  funnel  well  up  from  the 
bottom  so  that  the  plant  can  more 
readily  get  all  of  the  carbon  dioxid 
available  in  the  water.  Why  would 
boiled  water  be  undesirable  in  this 
experiment?  For  a  home-made 
glass  funnel,  crack  the  bottom  off 
a  narrow-necked  bottle  by  press- 
ing a  red-hot  poker  or  iron  rod 
against  it  and  leading  the  crack 
around  the  bottle.  Invert  a  test- 
tube  over  the  stem  of  the  fun- 
nel. In  sunlight  bubbles  of 
oxygen  will  arise  and  collect  in 
the  test-tube.  If  a  sufficient 
quantity  of  oxygen  has  collected, 
a  lighted  taper  inserted  in  the 
tube  will  glow  with  a  brighter  flame,  showing  the  presence  of 
oxygen  in  greater  quantity  than  in  the  air.  Shade  the  vessel. 
Are  bubbles  given  off  ?  For  many  reasons  it  is  impracticable 
to  continue  this  experiment  longer  than  a  few  hours.  90.  A 
simpler  experiment  may  be  made  if  one  of  the  waterweeds 
Cabomba  (water-lily  family)  is  available.  Tie  a  lot  of  branches 
together  so  that  the  basal  ends  shall  make  a  small  bundle.  Place 
these  in  a  large  vessel  of  spring  water,  and  insert  a  test-tube  of 
water  as  before  over  the  bundle.  The  bubbles  will  arise  from  the 
cut  surfaces.  Observe  the  bubbles  on  pond  scum  and  water- 
weeds  on  a  bright  day.       To  illustrate  the  results  of  respiration 


Fig.  122.  —  To    show  the  Escape 
of  Oxygen. 


LEAVES  — FUNCTION   OR    WORK 


103 


p^t, 


Fig.  123.  —  To  ILLUS- 
TRATE a  Product 
of  Respiration. 


Fig.  124.  —  Respira- 
tion of  Thick 
Roots. 


(CCX).    91.  In  a  jar  of  germinating  seeds  (Fig.  123)  place  carefully 
a  small  dish  of  liniewater  and  cover  tightly.     Put  a  similar  dish  in 

another  jar  of  about    the 

same  air  space.    After  a  few 

hours  compare  the  cloudi- 
ness or  precipitate  in  the 

two   vessels   of  limewater. 

92.    Or,    place    a  growing 

plant    in  a    deep    covered 

jar   away    from    the    light, 

and  after  a  few  hours  in- 
sert  a   lighted    candle   or 

splinter.      93.  Or,  perform 

a  similar  experiment  with 

fresh    roots    of    beets    or 

turnips    (Fig.     124)    from 

which  the  leaves  are  mostly 

removed.  In  this  case, 
the  jar  need  not  be  kept  dark ;  why  ? 
To  test  transpiration.  94.  Cut  a  succulent 
shoot  of  any  plant,  thrust  the  end  of  it  through  a  hole  in  a  cork, 
and  stand  it  in  a  small  bottle  of  water.  Invert  over  this  a  fruit 
jar,  and  observe 
that  a  mist  soon 
accumulates  on 
the  inside  of  the 
glass.  In  time 
drops  of  water 
form.  95.  The  ex- 
periment may  be 
varied  as  shown  in 
Fig.  125.  96.  Or, 
invert  the  fruit 
jar  over  an  entire 
plant,  3S  shown  in 
Fig.  126,  taking 
care  to  cover  the 
soil  with  oiled 
paper  or  rubber 
cloth  to  prevent 
evaporation  from 
the  soil.  97.  The 
test  may  also  be 
made  by  placing 
the  pot,  properly 
protected,  on  bal- 


FlG.    12?.  — TO    ILLUSTRATE    TRANSPIRATION. 


104 


PLANT  BIOLOGY 


ances,  and  the  loss  of  weight  will  be  noticed  (Fig.  127).     98.   Cu^l/ 
a  winter  twig,  seal  the  severed  end  with  wax,  and  allow  the  twig 
to  lie  several  days ;  it  shrivels.     There    must  be    some    upward 
movement   of   water  even  in   winter,    else    plants    would  shrivel 
and    die.       99.    To    illustrate   sap  pressure. 
The  upward    movement  of   sap  water  often 
takes  place  under  considerable  force.     The 
cause  of  this  force,  known  as  root  pressure, 
is  not  well  understood.     The  pressure  varies 
with    different   plants    and    under    different 
conditions.    To  illustrate  : 
cut  off  a  strong-growing 
small    plant    near 
the    ground.      By 
means  of  a  bit  of 
rubber  tube  attach 
a  glass  tube  with 
a  bore  of  approxi- 
mately the  diame- 
ter   of   the    stem. 
Pour    in    a    little 
water.     Observe 
the    rise     of     the 
water  due  to  the 
pressure  from  be- 
low  (Fig.    128).      Some   plants  yield   a  large 
amount  of  water  under   a   pressure    sufficient 
to  raise   a  column  several  feet ;    others  force 
out  little,  but  under  consider- 
able pressure    (less  easily  de- 
monstrated).    The  vital  pro- 
cesses {i.e.,  the  life  processes). 
100.  The  pupil 
having  studied 
roots,      stems, 
and    leaves, 
should   now 
be  able  to  de- 
scribe the  main 
vital  functions 
of  plants  :  what 
is  the  root  func- 
tion? stem  function?  leaf  function?   101.  What 
is  meant  by  the  "sap"?    102.  Where  and  how 
does  the  plant  secure  its  water?  oxygen?  car-     yli:    r2g  _]-<>  show 
bon?  hydrogen?  nitrogen?  sulfur?  potassium?  sap  Pressure. 


Fig.  126. — To  illustrate 
Transpiration. 


^ 


t  ig.  127.  —  Loss  of  Water. 


LEAVES—  FUNCTIOX  OR    WORK 


105 


calcium?  iron?  phosphorus?  103.  Where  is  all  the  starch  in  the 
world  made?  What  does  a  starch-factory  establishment  do? 
Where  are  the  real  starch  factories?  104.  In 
what  part  of  the  twenty-four  hours  do 
plants  grow  most  rapidly  in  length?  When 
is  food  formed  and  stored  most  rapidly? 
105.  Why  does  corn  or  cotton  turn  yellow 
in  a  long  rainy  spell?  106.  If  stubble, 
corn  stalks,  or  cotton  stalks  are  burned 
in  the  field,  is  as  much  plant-food  returned 
to  the  soil  as  when  they  are  plowed 
under?  107.  What  process  of  plants  is 
roughly  analogous  to  perspiration  of  ani- 
mals? 108.  What  part  of  the  organic 
world  uses  raw  mineral  for  food?  109.  Why 
is  earth  banked  over  celery  to  blanch  it? 
110.  Is  the  amount  of  water  transpired 
equal  to  the  amount  absorbed?  111.  Give 
some  reasons  why  plants  very  close  to  a 
house  may  not  thrive  or  may  even  die. 
112.  Why  are  fruit-trees  pruned  or  thinned 
out  as  in  Fig.  129?  Proper  balance  be- 
tween top  and  root.  113.  We  have  learned 
that  the  leaf  parts  and  the  root  parts  work 
together.  They  may  be  said  to  balance 
each  other  in  activities,  the  root  supplying  pIG<  I30  _  ^N  apple 
the  top  and  the  top  supplying  the  root  tree,  with  suggestions 
(how?).  If  half  the  roots  were  cut  from 
a  tree,  we  should  expect  to  reduce  the  top 
also,  particularly  if  the  tree  is  being  trans- 
planted. How  would  you  prune  a  tree  or 
bush  that  is  being  transplanted?     Fig.  130  may  be  suggestive 


as  to  pruning  when  it 
is  set  in  the  orchard.  At 
a  is  shown  a  pruned 
top. 


Fig.  129.  —  Before  and  after  Pruning. 


CHAPTER    XIV 


DEPENDENT   PLANTS 


Thus  far  we  have  spoken  of  plants  with  roots  and 
foliage  and  that  depend  on  themselves.  They  collect  the 
raw  materials  and  make  them  over  into  assimilable  food. 
They  are  independent.  Plants  without  green  foliage  can- 
not make  food ;  they 
must  have  it  made  for 
them  or  they  die. 
They  are  dependent.  A 
sprout  from  a  potato 
tuber  in  a  dark  cellar 
cannot  collect  and  elab- 
orate carbon  dioxid.  It 
lives  on  the  food  stored 
in  the  tuber. 

AH  plants  with  natu- 
rally white  or  blanched 
parts  are  dependent.  Their  leaves  do  not  develop.  They 
live  on  organic  matter  —  that  which  has  been  made  by  a 
plant  or  elaborated  by  an  animal.  The  dodder,  Indian 
pipe,  beech  drop,  coral  root  among  flower-bearing  plants, 
also  mushrooms  and  other  fungi  (Figs.  131,  132)  are  exam- 
ples. The  dodder  is  common  in  swales,  being  conspicuous 
late  in  the  season  from  its  thread-like  yellow  or  orange 
stems  spreading  over  the  herbage  of  other  plants.  One 
kind  attacks  alfalfa  and  is  a  bad  pest.  The  seeds  germi- 
nate in  the  spring,  but  as  soon  as  the  twining  stem  at- 

106 


Fig.  131.  —  A  Mushroom,  example  of  a  sapro- 
phytic plant.  This  is  the  edible  cultivated 
mushroom. 


DEPENDENT  PLANTS 


107 


Fig.  132.  — A  Parasitic 
Fungus,  magnified. 
The  mycelium,  or 
vegetative  part,  is 
shown  by  the  dotted- 
shaded  parts  ramify- 
ing in  the  leaf  tissue. 
The  rounded  haus- 
toria  projecting  into 
the  cells  are  also 
shown.  The  long 
fruiting  parts  of  the 
fungus  hang  from  the 
under  surface  of  the 
leaf. 


taches  itself  to  another  plant,  the  dod- 
der dies  away  at  the  base  and  becomes 
wholly  dependent.  It  produces  flowers 
in    clusters    and    seeds     itself    freely 

(Fig.   133)- 

Parasites  and  Saprophytes.  — A  plant 
that  is  dependent  on  a  living  plant  or 
animal  is  a  parasite,  and  the  plant  or 
animal  on  which  it  lives  is  the  host. 
The  dodder  is  a  true  parasite ;  so  are 
the  rusts,  mildews,  and  other  fungi  that 
attack  leaves  and  shoots  and  injure 
them. 

The  threads  of  a  parasitic  fungus 
usually  creep  through  the  intercellular 
spaces  in  the  leaf  or  stem  and  send 
suckers  (or  haustoria)  into  the  cells 
(Fig.  132).  The  threads  (or  the  hy- 
phae)  clog    the    air-spaces  of   the  leaf 


and  often  plug  the  stomates, 
and  they  also  appropriate  and 
disorganize  the  cell  fluids  ;  tJius 
they  injure  or  kill  their  host.  The  mass  of  hyphae 
of  a  fungus  is  called  mycelium.  Some  of  the 
hyphae  finally  grow  out  of  the  leaf  and  produce 
spores  or  reproductive  cells  that  an- 
swer the  purpose  of  seeds  in  distrib- 
uting the  plant  {b,  Fig.  132). 

A  plant  that  lives  on  dead  or  de- 
caying matter  is  a  saprophyte.  Mush- 
rooms (Fig.  131)  are  examples;  they 
live  on  the  decaying  matter  in  the 
soil.     Mold  on  bread  and  cheese  is  an 


io8 


PLANT  BIOLOGY 


example.  Lay  a  piece  of  moist  bread  on  a  plate  and 
invert  a  tumbler  over  it.  In  a  few  days  it  will  be  moldy. 
The  spores  were  in  the  air,  or  perhaps  they  had  already 
fallen  on  the  bread  but  had  not  had  opportunity  to  grow. 
Most  green  plants  are  unable  to  make  any  direct  use  of 
the  humus  or  vegetable  mold  in  the  soil,  for  they  are  not 

saprophytic.  The  shelf- 
fungi  (Fig.  134)  are  sap- 
rophytes. They  are  com- 
mon on  logs  and  trees. 
Some  of  them  are  perhaps 
partially  parasitic,  extend- 
ing the  mycelium  into  the 
wood  of  the  living  tree 
and  causing  it  to  become 
black-hearted  (Fig.  134). 
Some  parasites  spring 
from  the  ground,  as  other 
plants  do,  but  they  are 
parasitic  011  the  roots  of 
their  hosts.  Some  para- 
sites may  be  partially 
parasitic  and  partially 
saprophytic.  Many  (per- 
haps most)  of  these 
ground  saprophytes  are 
aided  in  securing  their 
food  by  soil  fungi,  which  spread  their  delicate  threads  over 
the  root-like  branches  of  the  plant  and  act  as  intermedi- 
aries between  the  food  and  the  saprophyte.  These  fungus- 
covered  roots  are  known  as  mycorrhizas  (meaning  "fungus 
root").  Mycorrhizas  are  not  peculiar  to  saprophytes. 
They  are  found  on  many  wholly  independent  plants,  as, 


Fig.  134. —  Tinder  Fungus  (Pohforus 
igniarius)  on  beech  log.  The  external 
part  of  the  fungus  is  shown  below;  the 
heart-rot  injury  above. 


DEPENDENT  PLANTS 


109 


Fig.  135. —  Bacteria  of  Several 
Forms,  much  magnified. 


for  example,  the  heaths,  oaks,  apples,  and  pines.  It  is 
probable  that  the  fungous  threads  perform  some  of  the 
offices  of  root-hairs  to  the 
host.  On  the  other  hand, 
the  fungus  obtains  some 
nourishment  from  the 
host.  The  association 
seems  to  be  mutual. 

Saprophytes  break 
down  or  decompose  or- 
ganic substances.  Chief 
of  these  saprophytes  are 
many  microscopic  organ- 
isms known  as  bacteria  (Fig.  135).  These  innumerable 
organisms  are  immersed  in  water  or  in  dead  animals  and 

plants,  and  in  all  manner  of 
moist  organic  products.  By 
breaking  down  organic 
combinations,  they  produce 
decay.  Largely  through 
their  agency,  and  that  of 
many  true  but  microscopic 
fungi,  all  things  pass  into 
soil  and  gas.  Thus  are  the 
bodies  of  plants  and  animals 
removed  and  the  continuing 
round  of  life  is  maintained. 
Some  parasites  arc  grecn- 
leavcd.  Such  is  the  mistle- 
toe (Fig.  136).  They  anchor 
themselves  on  the  host  and 

absorb    its    juices,  but   they 
Fig.  136. —  American  Mistletoe  j   _  J 

growing  on  a  Walnut  Branch.       also     appropriate     and     use 


I  I O  PLANT  BIOL OGY 

the  carbon  dioxid  of  the  air.  In  some  small  groups  of 
bacteria  a  process  of  organic  synthesis  has  been  shown  to 
take  place. 

Epiphytes.  —  To  be  distinguished  from  the  dependent 
plants  are  those  that  grow  on  other  plants  without  taking 
food  from  them.  These  are  green-leaved  plants  whose 
roots  burrow  in  the  bark  of  the  host  plant  and  perhaps 
derive  some  food  from  it,  but  which  subsist  chiefly  on 
materials  that  they  secure  from  air  dust,  rain  water,  and 
the  air.  These  plants  are  epiphytes  (meaning  "upon 
plants")  or  air  plants. 

Epiphytes  abound  in  the  tropics.  Certain  orchids  are 
among  the  best  known  examples  (Fig.  37).  The  Spanish 
moss  or  tillandsia  of  the  South  is  another.  Mosses  and 
lichens  that  grow  on  trees  and  fences  may  also  be  called 
epiphytes.  In  the  struggle  for  existence,  the  plants 
probably  liave  been  driven  to  these  special  places  in  which 
to  find  opportunity  to  grow.  Plants  grow  where  they 
must,  not  where  they  will. 

Suggestions.  — 114.  Is  a  puffball  a  plant  ?  Why  do  you 
think  so?  115.  Are  mushrooms  ever  cultivated,  and  where 
and  how?  116.  In  what  locations  are  mushrooms  and  toadstools 
usually  found?  (There  is  really  no  distinction  between  mush- 
rooms and  toadstools.  They  are  all  mushrooms.)  117.  What 
kinds  of  mildew,  blight,  and  rust  do  you  know?  118.  How  do 
farmers  overcome  potato  blight?  Apple  scab?  Or  any  other 
fungous  "plant  disease"?  119.  How  do  these  things  injure 
plants?  120.  What  is  a  plant  disease?  121.  The  pupil  should 
know  that  every  spot  or  injury  on  a  leaf  or  stem  is  caused  by 
something,  —  as  an  insect,  a  fungus,  wind,  hail,  drought,  or  other 
agency.  How  many  uninjured  or  perfect  leaves  are  there  on 
the  plant  growing  nearest  the  schoolhouse  steps?  122.  Give 
formula  for  Bordeaux  mixture  and  tell  how  and  for  what  it  is  used. 


CHAPTER   XV 


WINTER   AND   DORMANT   BUDS 


A  bud  is  a  growing  point,  terminating  an  axis  either  long 
or  short,  or  being  the  starting  point  of  an  axis.  All 
branches  spring  from  buds.  In  the  growing  season  the 
bud  is  active ;  later  in  the  season  it  ceases  to  increase  the 
axis  in  length,  and  as  winter  approaches  the  growing 
point  becomes  more  or  less  thickened  and  covered  by  pro- 
tecting scales,  in  preparation  for  the  long  resting  season. 
This  resting,  dormant,  or  winter  body  is  what  is  commonly 
spoken  of  as  a  "bud."  A  winter  bud  may  be  defined 
as  an  inactive  covered  growing  pointy  waiting  for  spring. 

Structurally,  a  dormant  bud  is  a  shortened  axis  or  branch, 
bearing  miniature  leaves  or  flowers  or  both,  and  protected 
by  a  covering.  Cut  in  two,  lengthwise,  a 
bud  of  the  horse-chestnut  or  other  plant 
that  has  large  buds.     With  a  pin  separate 

the  tiny  leaves.    Count  them. 

Examine  the  big  bud  of  the 

rhubarb  as  it  lies  under  the 

ground  in  late  winter  or  early 

spring  ;  or  the  crown  buds  of 

asparagus,  hepatica,  or  other 

early    spring    plants.      Dis- 
sect large  buds  of  the  apple 

and  pear  (Figs.  137,  138). 
The   bud  is  protected  by  firm    and  dry   scales.      These 
scales  are  modified   leaves.     The  scales  fit  close.     Often 

in 


Fig.  137.  —  Bud 
of  Apricot, 
showing  the 
miniature 
leaves. 


Fig.  138.  —  Bud  of 
Pear,  showing 
both  leaves  and 
fl  o  w  e  r  s.  The 
latter  are  the  lit- 
tle knobs  in  the 
center. 


I  12 


PLANT  BIOLOGY 


the  bud  is  protected  by  varnish  (sec  horse-chestnut  and 
the  balsam  poplars).  Most  winter  buds  are  more  or  less 
woolly.  Examine  them  under  a  lens.  As  we  might 
expect,  bud  coverings  are  most  prominent  in  cold  and  dry 
climates.  Sprinkle  water  on  velvet  or  flannel,  and  note 
the  result  and  give  a  reason. 

All  winter  buds  give  rise  to  branches,  not  to  leaves  alone; 
that  is,  the  leaves  are  borne  on  the  lengthening  axis. 
Sometimes  the  axis,  or  branch,  remains  very  short,  —  so 
short  that  it  may  not  be  noticed.  Sometimes  it  grows 
several  feet  long. 

Whether  the  branch  grows  large  or  not  depends  on  the 
chance  it  has, — position  on  the  plant,  soil,  rainfall,  and 
many  other  factors.  The  new  shoot  is  the 
unfolding  and  enlarging  of  the  tiny  axis 
and  leaves  that  we  saw  in  the  bud.  If  the 
conditions  are  congenial,  the  shoot  may 
form  more  leaves  than  were  tucked  away 
in  the  bud.  The  length  of  the  shoot  usu- 
ally depends  more  on  the  lengths  of  the 
internodes  than  on  the  number  of  leaves. 

Where  Buds  are.  —  Buds  arc  borne  in  the 
axils  of  the  leaves,  —  in  the  acute  angle 
that  the  leaf  makes  with  the  stem.  When 
the  leaf  is  growing  in  the  summer,  a  bud 
is  forming  above  it.  When  the  leaf  falls, 
scars.  — Aiianthus.  the  bud  remains,  and  a  scar  marks  the 
place  of  the  leaf.  Fig.  139  shows  the  large  leaf-scars  of 
aiianthus.  Observe  those  on  the  horse-chestnut,  maple, 
apple,  pear,  basswood,  or  any  other  tree  or  bush. 

Sometimes  two  or  more  buds  are  borne  in  one  axil ;  the 
extra  ones  are  accessory  or  supernumerary  buds.  Observe 
them    in    the    Tartarian  honeysuckle  (common  in  yards), 


Fig.  139.  —Leaf- 


WINTER  AND  DORMANT  BUDS 


113 


walnut,  butternut,  red  maple,  honey  locust,  and  sometimes 
in  the  apricot  and  peach. 

If  the  bud  is  at  the  end  of  a  shoot,  however  short  the 
shoot,  it  is  called  a  terminal  bud.  //  continues  the  grozvth 
of  the  axis  in  a  direct  line.  Very  often 
three  or  more  buds  are  clustered  at  the  tip 
(Fig.  140);  and  in  this  case  there  may  be 
more  buds  than  leaf  scars.  Only  one  of 
them,  however,  is  strictly  terminal. 

A  bud  in  the  axil  of  a  leaf  is  an  axillary 
or  lateral  bud.  Note  that  there  is  normally 
at  least  one  bud  in  the  axil  of  every  leaf  on 
a  tree  or  shrub  in  late  summer  and  fall.  The 
axillary  buds,  if  they  grow,  are  the  starting 
points  of  new  shoots  the  following  season.  If 
a  leaf  is  pulled  off  early  in  summer,  what 
will  become  of  the  young  bud  in  its  axil  ? 
Try  this. 

Bulbs  and  cabbage  heads  may  be  likened  to  buds ;  that  is, 
they  are  condensed  stems,  with  scales  or  modified  leaves 

densely  overlapping 

- 


Fig.  140.   -  Ter- 
minal Bud 
between  two 
other  Buds. 
—  Currant. 


and        forming       a 
rounded  body  (Fig. 
141).      They    differ 
from  true  buds,  how- 
ever,    in     the     fact 
that    they  are    con- 
densations of  whole 
main    stems    rather 
than  embryo  stems 
borne  in  the  axils  of 
leaves.     But  bulblets  (as  of  tiger  lily)  may  be  scarcely  dis- 
tinguishable from  buds  on  the  one  hand  and   from  bulbs 
1 


Fig.  141.  —  A  Gigantic  Bud.  —  Cabbage. 


Ii4 


/'/..-/ XT  BIOLOGY 


W\\b 


Fig.  142.  — 
Fruit-bud 
of  Pear. 


on  the   other.     Cut  a  cabbage  head   in   two,  lengthwise, 
and  see  what  it  is  like. 

The  buds  that  appear  on  roots  are  unusual  or  abnormal, 

— they  occur  only  occasionally  and  in  no  definite  order. 

Buds  appearing  in  unusual  places  on  any  part  of  the  plant 

are  called  adventitious  buds.     Such  usually  are  the  buds 

that  arise  when  a  large  limb   is  cut   off,   and 

from  which  suckers 

or     water    sprouts 

arise. 

How  Buds  Open. 
—  When  the  bud 
swells,  the  scales 
are  pushed  apart, 
the  little  axis  elon- 
gates and  pushes 
out.  In  most  plants 
the  outside  scales 
fall  very  soon,  leaving  a  little  ring  of  scars. 
With  terminal  buds,  this  ring  marks  the  end 
of  the  year's  growth:  how? 
Notice  peach,  apple,  plum, 
willow,  and  other  plants.  In 
some  others,  all  the  scales  grow  for  a  time, 
as  in  the  pear  (Figs.  142,  143,  144).  In 
other  plants  the  inner  bud  scales  become 
green  and  almost  leaf-like.  See  the  maple 
and  hickory. 

Sometimes     Flowers     come    out    of    the 
Buds.  —  Leaves  may  or  may  not  accompany 
the  flowers.     We  saw  the  embryo  flowers  in 
Fig.  145.  — Open-     p-      r,g      The  bud  is  shown  again  in  Fig. 

ING     OF      THE  °  00 

Pear-bud.  142.      In  Fig.  143  it  is  opening.     In  Fig.  145 


Fig.  143. —  The 
opening  OF 
the  Pear 
Fruit-bud. 


Fig.  144.  —  open- 
ing Pear 
Leaf-bud. 


WINTER   AND   DORMANT  BUDS 


"5 


it  is  more  advanced,  and  the  woolly  unformed  flowers  are 
appearing.     In  Fig.  146  the  growth  is  more  advanced. 


Fig.  146.  — A  sin- 
gle Flower 
in  the  Pear 
cluster,  as 
seen  at  7  A.M. 
on  the  day  of 
its  opening.  At 
10  o'clock  it 
will  be  fully  ex- 
panded. 


Fig.  147. —  The 

opening  of 

the  flovver- 

BUD  OF 

Apricot. 


Fig.  148. —  Apricot 
Flower-bud,  enlarged. 


leaf-buds. 


Buds  that  contain  or 
produce  only  leaves  are 
Those  which  contain  only  flowers  are  flower 


buds  or  fruit-buds.     The  latter  occur  on 
peach,  almond,  apricot,  and  many  very 
early  spring-flowering  plants.    The 
single  flower  is  emerging  from  the 
apricot  bud  in  Fig.  147.     A  longi- 
tudinal section  of  this  bud,  enlarged,  is 
shown  in  Fig.  148.     Those  that  contain 
both  leaves  and  flowers  are  mixed  buds, 
as  in  pear,  apple,  and  most  late  spring- 
flowering  plants. 

Fruit  buds  are  usually  thicker  or 
stouter  than  leaf-buds.  They  are  borne 
in  different  positions  on  different  plants. 
In  some  plants  (apple,  pear)  they  are 
on  the  ends  of  short  branches  or  spurs; 
in  others  (peach,  red   maple)  they  are 

along   the  sides  of   the  last    year's 

&  J  Fig.  149. —  Fruit-buds 

growths.       In   Fig.   149    are    shown      and  leaf-budsof  pear. 


n6 


PLANT  BIOLOGY 


three  fruit-buds  and  one  leaf-bud  on  E,  and  leaf-buds  on 
A.     See  also  Figs.  150,  151,  152,  153,  and  explain. 


Fig.  150. —  Fruit-buds  of  Apple 
on  Spurs  :  a  dormant  bud  at 
the  top. 


Fig.  151.  — Cus- 
ter of  Fruit- 
buds  of  SWEET 
Cherry,  with 
one  pointed 
leaf-bud  in  cen- 
ter. 


Fig.  152.  —  Two 
Fruit-buds 
of      Peach 

with    a     leaf- 
bud  between. 


Fig.  153. —  Opening  ok  Leaf-buds  and  Flower-buds  of  Apple. 

"The  burst  of  spring"  means  in  large  part  the  opening  of 
the  buds.  Everything  was  made  ready  the  fall  before.  The 
embryo  shoots  and  flowers  were  tucked  away,  and  the  food 
was  stored.  The  warm  rain  falls,  and  the  shutters  open 
and  the  sleepers  wake  :  the  frogs  peep  and  the  birds  come. 

Arrangement  of  Buds. — We  have  found  that  leaves  are 
usually  arranged  in  a  definite  order ;  buds  are  borne  in  the 
axils  of    leaves :    therefore  buds   must   exhibit  phyllotaxy. 


WINTER  AND  DORMANT  BUDS 


117 


Moreover,  branches  grow  from  buds:  branches,  therefore, 
should  show  a  definite  arrangement;  usually,  however,  they 
do  not  show  this  arrangement  because  not  all  the  buds grozv 
and  not  all  the  branches  live.  (See  Chaps.  II  and  III.) 
It  is  apparent,  however,  that  the  mode  of  arrangement  of 
buds  determines  to  some  extent  the  form  of  the  tree:  com- 
pare bud  arrangement  in  pine  or  fir  with  that  in  maple  or 
apple. 


FIG.  154.  —  Oak  Spray.      How  are  the  leaves  borne  with  reference  to 
the  annual  growths  ? 

The  uppermost  buds  on  any  twig,  if  they  are  well 
matured,  are  usually  the  larger  and  stronger  and  they  are 
the  most  likely  to  grow  the  next  spring;  therefore,  branches 
tend  to  be  arranged  in  tiers  (particularly  well  marked  in 
spruces  and  firs).     See  Fig.  154  and  explain  it. 

Winter  Buds  show  what  has  been  the  Effect  of  Sunlight. — 
Buds  are  borne  in  the  axils  of  the  leaves,  and  the  size  of 
vigor  of  the  leaf  determines  to  a  large  extent  the  size  of  the 
bud.  Notice  that,  in  most  instances,  the  largest  buds  are 
nearest  the  tip  (Fig.  157).  If  the  largest  ones  are  not 
near  the  tip,  there  is  some  special  reason  for  it.  Can  you 
state  it  ?     Examine  the  shoots  on  trees  and  bushes. 


1 1 S  PLANT  BIOLOGY 

SUGGESTIONS.  —  Some  of  the  best  of  all  observation  lessons  are 
those  made  on  dormant  twigs.  There  are  many  things  to  be 
learned,  the  eyes  are  trained,  and  the  specimens  are  everywhere 
accessible.  123.  At  whatever  time  of  year  the  pupil  takes  up  the 
study  of  branches,  he  should  look  for  three  things:  the  ages  of 
the  various  parts,  the  relative  positions  of  the  buds  and  leaves,  the 
different  sizes  of  similar  or  comparable  buds.  If  it  is  late  in 
spring  or  early  in  summer,  he  should  watch  the  development  of 
the  buds  in  the  axils,  and  he  should  determine  whether  the 
strength  or  size  of  the  bud  is  in  any  way  related  to  the  size  and 
vigor  of  the  subtending  (or  supporting)  leaf.  The  sizes  of  buds 
should  also  be  noted  on  leafless  twigs,  and  the  sizes  of  the  former 
leaves  may  be  inferred  from  the  size  of  the  leaf-scar  below  the 
bud.  The  pupil  should  keep  in  mind  the  fact  of  the  struggle 
for  food  and  light,  and  its  effects  on  the  developing  buds. 
124.  The  bud  and  the  branch.  A  twig  cut  from  an  apple  tree 
in  early  spring  is  shown  in  Fig.  155.  The  most  hasty  obser- 
vation shows  that  it  has  various  parts,  or  members.  It  seems  to 
be  divided  at  the  point  /  into  two  parts.  It  is  evident  that  the 
part  from/  to  //  grew  last  year,  and  that  the  part  below/  grew 
two  years  ago.  The  buds  on  the  two  parts  are  very  unlike, 
and  these  differences  challenge  investigation.  —  In  order  to  under- 
stand this  seemingly  lifeless  twig,  it  will  be  necessary  to  see  it  as 
it  looked  late  last  summer  (and  this  condition  is  shown  in  Fig. 
156).  The  part  from  /  to  //, —  which  has  just  completed  its 
growth,  —  is  seen  to  have  its  leaves  growing  singly.  In  every  axil 
(or  angle  which  the  leaf  makes  when  it  joins  the  shoot)  is  a  bud. 
The  leaf  starts  first,  and  as  the  season  advances  the  bud  forms  in 
its  axil.  When  the  leaves  have  fallen,  at  the  approach  of  winter, 
the  buds  remain,  as  seen  in  Fig.  155.  Every  bud  on  the  last 
year's  growth  of  a  winter  twig,  therefore,  marks  the  position 
occupied  by  a  leaf  when  the  shoot  was  growing.  —  The  part  below 
/  in  Fig.  156,  shows  a  wholly  different  arrangement.  The  leaves 
are  two  or  more  together  (aaaa),  and  there  are  buds  without 
leaves  (bbbb).  A  year  ago  this  part  looked  like  the  present  shoot 
from  /  to  h,  —  that  is,  the  leaves  were  single,  with  a  bud  in  the 
axil  of  each.  It  is  now  seen  that  some  of  these  bud-like  parts 
are  longer  than  others,  and  that  the  longest  ones  are  those  which 
have  leaves.  It  must  be  because  of  the  leaves  that  they  have 
increased  in  length.  The  body  c  has  lost  its  leaves  through  some 
accident,  and  its  growth  has  ceased.  In  other  words,  the  parts 
at  aaaa  are  like  the  shoot  ///,  except  that  they  are  shorter,  and 
they  are  of  the  same  age.  One  grew  from  the  end  or  terminal 
bud  of  the  main  branch,  and  the  others  from  the  side  or  lateral 
buds.  Parts  or  bodies  that  bear  leaves  are,  therefore,  branches. 
—  The  buds  at  bbbb  have  no  leaves,  and  they  remain  the  same 


WINTER   AND   DORMANT  BUDS 


119 


size  that  they  were  a  year  ago.    They  are  dormant.    The  only  way 
for  a  mature  bud  to  grow  is  by  making  leaves  for  itself,  for  a  leaf 


W 


Fig.  155.  —  An 
Apple  Twig. 


Fig.  156. —  Same  twig  before  leaves  fell. 


will  never  stand  below  it  again.     The  twig,  therefore,  has  buds  of 
two  ages,  —  those  at  bbbb  are  two  seasons  old,  and  those  on  the 


120  PLANT  BI0lor,y 

tips,  of  all  the  branches  (aaaa,  h),  and  in  the  axil  of  every  leaf, 
are  one  season  old.  It  is  only  the  terminal  buds  that  are  not 
axillary.  When  the  hud  begins  to  grow  and  to  put  forth  leaves, 
it  gives  rise  to  a  branch,  which,  in  its  turn,  heats  buds.  —  It  will 
now  be  interesting  to  determine  why  certain  buds  gave  rise  to 
branches  and  why  others  remained  dormant.  The  strongest 
shoot  or  branch  of  the  year  is  the  terminal  one  (///)•  The 
next  in  strength  is  the  uppermost  lateral  one,  and  the  weakest 
shoot  is  at  the  base  of  the  twig.  The  dormant  buds  are  on  the 
under  side  (for  the  twig  grew  in  a  horizontal  position).  All  this 
suggests  that  those  buds  grew  which  had  the  best  chance,  —  the 
most  sunlight  and  room.  There  were  too  many  buds  for  the  space, 
and  in  the  struggle  for  existence  those  that  had  the  best  oppor- 
tunities made  the  largest  growths.  This  struggle  for  existence 
began  a  year  ago,  however,  when  the  buds  on  the  shoot  below/ 
were  forming  in  the  axils  of  the  leaves,  for  the  buds  near  the  tip 
of  the  shoot  grew  larger  and  stronger  than  those  near  its  base. 
The  growth  of  one  year,  therefore,  is  very  largely  determined  by 
the  conditions  under  which  the  buds  were  formed  the  previous 
year.  Other  bud  characters.  125.  It  is  easy  to  see  the  swelling 
of  the  buds  in  a  room  in  winter.  Secure  branches  of  trees  and 
shrubs,  two  to  three  feet  long,  and  stand  them  in  vases  or  jars, 
as  you  would  flowers.  Renew  the  water  frequently  and  cut  off 
the  lower  ends  of  the  shoots  occasionally.  In  a  week  or  two  the 
buds  will  begin  to  swell.  Of  red  maple,  peach,  apricot,  and  other 
very  early-flowering  things,  flowers  may  be  obtained  in  ten  to 
twenty  days.  126.  The  shape,  size,  and  color  of  the  winter  buds 
are  different  in  every  kind  of  plant.  By  the  buds  alone  botanists 
are  often  able  to  distinguish  the  kinds  of  plants.  Even  such 
similar  plants  as  the  different  kinds  of  willows  have  good  bud 
characters.  127.  Distinguish  and  draw  fruit-buds  of  apple,  pear, 
peach,  plum,  and  other  trees.  If  different  kinds  of  maples  grow 
in  the  vicinity,  secure  twigs  of  the  red  or  swamp  maple,  and  the 
soft  or  silver  maple,  and  compare  the  buds  with  those  of  the  sugar 
maple  and  Norway  maple  :    What  do  you  learn? 


Fig.  157. —Buds  of  the  Hickory. 


CHAPTER  XVI 

BUD   PROPAGATION 

We  have  learned  (in  Chap.  VI)  that  plants  propagate 
by  means  of  seeds.  They  also  propagate  by  means  of  bud 
parts,  —  as  rootstocks  (rhizomes),  roots,  runners,  layers-,  bulbs. 
The  pupil  should  determine  how  any  plant  in  which  he  is 
interested  naturally  propagates  itself  (or  spreads  its  kind). 
Determine  this  for  raspberry,  blackberry,  strawberry,  June- 
grass  or  other  grass,  nut-grass,  water  lily,  May  apple  or 
mandrake,  burdock,  Irish  potato,  sweet  potato,  buckwheat, 
cotton,  pea,  corn,  sugar-cane,  wheat,  rice. 

Plants  may  be  artificially  propagated  by  similar  means, 
as  by  layers,  cuttings,  and  grafts.  The  last  two  we  may 
discuss  here. 

Cuttings  in  General. — A  bit  of  a  plant  stuck  into  the 
ground  stands  a  chance  of  growing;  and  this  bit  is  a  cutting. 
Plants  have  preferences,  however,  as  to  the  kind  of  a  bit 
which  shall  be  used,  but  there  is  no  way  of  telling  what  this 
preference  is  except  by  trying.  In  some  instances  this  prefer- 
ence has  not  been  discovered,  and  we  say  that  the  plant 
cannot  be  propagated  by  cuttings. 

Most  plants  prefer  that  the  cutting  be  made  of  the  soft 
or  growing  parts  (called  "wood"  by  gardeners),  of  which 
the  "slips"  of  geranium  and  coleus  are  examples.  Others 
grow  equally  well  from  cuttings  of  the  hard  or  mature  parts 
or  wood,  as  currant  and  grape;  and  in  some  instances  this 
mature  wood  may  be  of  roots,  as  in  the  blackberry.  In 
some  cases  cuttings  are  made  of   tubers,  as  in  the  Irish 


122 


PLANT  BIOLOGY 


potato  (Fig.  60).  Pupils  should  make  cuttings  now  and 
then.  It  they  can  do  nothing  more,  they  can  make  cut- 
tings of  potato,  as  the  farmer  does;  and  they  can  plant 
them  in  a  box  in  the  window. 

The  Softwood  Cutting. — The  softwood  cutting  is  made 
from  tissue  that  is  still  growing,  or  at  least  from  that 
which  is  not  dormant.     It  comprises  one  or  two  joints,  with 


Fig.  158.  —  Geranium  Cutting.  Fig.  159. —Rose  Cutting. 

a  leaf  attached  (Figs.  158,  159).  It  must  not  be  allowed 
to  wilt.  Therefore,  it  must  be  protected  from  direct  sun- 
light and  dry  air  until  it  is  well  established ;  and  if  it  has 
many  leaves,  sonic  of  than  should  be  removed,  or  at  least  cut 
in  two,  in  order  to  reduce  the  evaporating  surface.  The 
soil  should  be  uniformly  moist.  The  pictures  show  the 
depth  to  which  the  cuttings  are  planted. 

For  most  plants,  the  proper  age  or  maturity  of  wood  for 
the  making  of  cuttings  may  be  determined  by  giving  the 
twig  a  quick  bend:  if  it  snaps  and  hangs  by  the  bark,  it  is  in 
proper  condition ;  if  it  bends  without  breaking,  it  is  too 
young  and  soft  or  too  old ;  if  it  splinters,  it  is  too  old  and 
woody.  The  tips  of  strong  upright  shoots  usually  make 
the  best  cuttings.  Preferably,  each  cutting  should  have  a 
joint  or  node  near  its  base;  and  if  the  internodes  are  very 
short  it  may  comprise  two  or  three  joints. 


B  I'D   PR  OP  A  GA  TIOX 


123 


The  stem  of  the  cutting  is  inserted  one  third  or  more  its 
length  in  clean  sand  or  grave/,  and  the  earth  is  pressed  firmly 
about  it.  A  newspaper  may  be  laid  over  the  bed  to  ex- 
clude the  light  —  if  the  sun  strikes  it — and  to  prevent  too 
rapid  evaporation.  The  soil  should  be  moist  clear  through, 
not  on  top  only. 

Loose  sandy  or  gravelly  soil  is  used.  Sand  used  by 
masons  is  good  material  in  which  to  start  most  cuttings;  or 
fine  gravel  —  sifted  of  most 


,4— -k; 


m 


Fig.  160.  —  Cutting-box. 


of  its  earthy  matter  —  may 
be  used.  Soils  are  avoided 
which  contain  much  decay- 
ing organic  matter,  for  these 
soils  are  breeding  places  of 
fungi,  which  attack  the  soft 
cutting  and  cause  it  to  "  damp 
off,"  or  to  die  at  or  near  the  surface  of  the  ground.  If  the 
cuttings  are  to  be  grown  in  a  window,  put  three  or  four 
inches  of  the  earth  in  a  shallow  box  or  a  pan.  A  soap 
box  cut  in  two  lengthwise,  so  that  it  makes  a  box  four  or 
five  inches  deep  —  as  a  gardener's  flat  —  is  excellent  (Fig. 
160).     Cuttings  of   common   plants,  as   geranium,   coleus, 

fuchsia,  carnation,  are  kept  at  a 
living-room  temperature.  As  long 
as  the  cuttings  look  bright  and 
green,  they  are  in  good  condition. 
It  may  be  a  month  before  roots 
form.  When  roots  have  formed, 
the  plants  begin  to  make  new 
leaves  at  the  tip.  Then  they  may 
be  transplanted  into  other  boxes 
of  into  pots.  The  verbena  in  Fig.  161  is  just  ready  for 
transplanting. 


Fig.  161.  —  Verbena  Cutting 
ready  for  transplan  i  [ng. 


124 


PL. I. XT  BIOLOGY 


Fig.  162.  —  Old  Geranium  Plant 
cut  back  to  make  it  throw  out 
Shoots  from  which  Cuttings 
can  be  made. 

dovv  plants  are  those  which 
old.  The  gera  n  ium 
and  fuchsia  cut- 
tings which  arc 
made  in  fanuaiy, 
February,  or  March 
will  give  compact 
blooming  plants  for 
the  next  winter  ; 
and  thereafter  new 
ones  should  take 
their  places    (Fig. 

163). 

The  Hardwood 
Cutting.  —  Best  re- 
sults with  cuttings 
of  mature  wood  are 


It  is  not  always  easy  to 
find  growing  shoots  from 
which  to  make  the  cut- 
tings. The  best  practice, 
in  that  case,  is  to  cut  back 
an  old  plant,  then  keep  it 
warm  and  well  watered, 
and  thereby  force  it  to  thro:.' 
out  new  shoots.  The  old 
geranium  plant  from  the 
window  garden,  or  the  one 
taken  up  from  the  lawn 
bed,  may  be  treated  this 
way  (see  Fig.  162).  The 
best  plants  of  geranium 
and  coleus  and  most  win- 
are  not  more  than  one  year 


Fig.  163.  —  Early  Winter  Geranium,  from 

a  spring  cutting. 


BUD  PROPAGATION 


125 


secured  when  the  cuttings  are  made  in  the  fall  and  then 
buried  until  spring  in  sand  in  the  cellar.  These  cuttings 
are  usually  six  to  ten  inches  long.  They  are  not  idle  while 
they  rest.  The  lower  end  calluses  or  heals,  and  the  roots 
form  more  readily  when  the  cutting  is  planted  in  the 
spring.  But  if  the  proper  season  has  passed,  take  cuttings 
at  any  time  in  winter,  plant  them  in  a  deep 
box  in  the  window,  and  watch.  They  will 
need  no  shading  or  special  care.  Grape, 
currant,  gooseberry,  willow,  and  poplar 
readily  take  root  from  the  hardwood. 
Fig.  164  shows  a  currant  cutting.  It  has 
only  one  bud  above  the  ground. 

The  Graft.  —  When  the  cutting  is  inserted 
in  a  plant  rather  than  in  the  soil,  it  is  a 
graft ;  and  the  graft  may  grow.  In  this 
case  the  cutting  grows  fast  to  the  other 
plant,  and  the  two  become  one.  When 
the  cutting  is  inserted  in  a  plant,  it  is  no 
longer  called  a  cutting,  but  a  cion;  and  the 
plant  in  which  it  is  inserted  is  called  the 
stock.  Fruit  trees  are  grafted  in  order 
that  a  certain  variety  or  kind  may  be  per- 
petuated, as  a  Baldwin  or  Ben  Davis  vari- 
ety of  apple,  Seckel  or  Bartlett  pear,  Navel 
or  St.  Michael  orange. 

Plants  have  preferences  as  to  the  stocks  on  which  they 
will  grow ;  but  zve  can  find  out  what  their  choice  is  only 
by  making  the  experiment.  The  pear  grows  well  on  the 
quince,  but  the  quince  does  not  thrive  on  the  pear. 
The  pear  grows  on  some  of  the  hawthorns,  but  it  is  an 
unwilling  subject  on  the  apple.  Tomato  plants  will  grow 
on    potato    plants    and    potato    plants    on    tomato    plants. 


Fig.  164.  — Cur- 
rant Cutting. 


126  PLANT  BIOI.OCY 

When  the  potato  is  the  root,  both  tomatoes  and  potatoes 
may  be  produced,  although  the  crop  will  be  very  small ; 
when  the  tomato  is  the  root,  neither  potatoes  nor  tomatoes 
will  be  produced.  Chestnut  will  grow  on  some  kinds  of 
oak.  In  general,  one  species  or  kind  is  grafted  on  the 
same  species,  as  apple  on  apple,  pear  on  pear,  orange  on 
orange. 

The  forming,  growing  tissue  of  the  stem  (on  the  plants 
we  have  been  discussing)  is  the  cambium  (Chap.  X),  lying 
on  the  outside  of  the  woody  cylinder  beneath  the  bark.  In 
order  that  union  may  take  place,  the  cambium  of  the  cion 
and  of  the  stock  must  come  together.  Therefore  the  cion 
is  set  in  the  side  of  the  stock.  There  are  many  ways  of 
shaping  the  cion  and  of  preparing  the  stock  to  receive  it. 
These  ways  are  dictated  largely  by  the  relative  sizes  of 
cion  and  stock,  although  many  of  them  are  matters  of 
personal  preference.  The  underlying  principles  are  two  : 
securing  close  contact  between  the  cambiums  of  cion  and 
stock ;  covering  the  wounded  surfaces  to  prevent  evapora- 
tion and  to  protect  the  parts  from  disease. 

On  large  stocks  the  commonest  form  of  grafting  is  the 
cleft-graft.  The  stock  is  cut  off  and  split ;  and  in  one  or 
both  sides  a  wedge-shaped  cion  is  firmly  inserted.  Fig. 
165  shows  the  cion  ;  Fig.  166,  the  cions  set  in  the  stock; 
Fig.  167,  the  stock  waxed.  It  will  be  seen  that  the  lower 
bud — that  lying  in  the  wedge  —  is  covered  by  the  wax; 
but  being  nearest  the  food  supply  and  least  exposed  to 
weather,  it  is  the  most  likely  to  grow  :  it  will  push  through 
the  wax. 

Cleft-grafting  is  practiced  in  spring,  as  growth  begins. 
The  cions  are  cut  previously,  when  perfectly  dormant,  and 
from  the  tree  which  it  is  desired  to  propagate.  The  cions 
are  kept  in  sand  or  moss  in  the  cellar.     Limbs  of  various 


BUD   PROPAGATION 


127 


sizes  may  be  cleft-grafted,  —  from  one  half  inch  up  to  four 
inches  in  diameter ;  but  a  diameter  of  one  to  one  and  one 
half  inches  is  the  most  convenient  size.  All  the  leading 
or  main  branches  of  a  tree  top  may  be  grafted.  If  the 
remaining  parts  of  the  top  are  gradually  cut  away  and 
the  cions  grow  well,  the  entire  top  will  be  changed  over  to 
the  new  variety. 


Fig.  165.- 
Cion  OF 
Apple. 


Fig.  166.  — The 
Cion  Inserted. 


Fig.  167.  — The 
Parts  Waxed. 


Another  form  of  grafting  is  known  as  budding.  In  this 
case  a  single  bud  is  used,  and  it  is  slipped  underneath  the 
bark  of  the  stock  and  securely  tied  (not  waxed)  with  soft 
material,  as  bass  bark,  corn  shuck,  yarn,  or  raffia  (the  last 
a  commercial  palm  fiber).  Budding  is  performed  when  the 
bark  of  the  stock  will  slip  or  peel  (so  that  the  bud  can  be 
inserted),  and  when  the  biul  is  mature  enough  to  grow. 
Usually  budding  is  performed  in  late  summer  or  early 
fall,  when  the  winter  buds  are  well  formed ;  or  it  may  be 
practiced  in  spring  with  buds  cut  in  winter.  In  ordinary 
summer  budding  (which  is  the  usual  mode)  the  "bud"  or 
cion  forms  a  union  with  the  stock,  and  then  lies  dormant 
till  the  following  spring,  as  if  it  were  still  on  its  own  twig. 


I2J 


PI.AXT  BIOLOGY 


Budding  is  mostly  restricted  to  young  trees  in  the  nursery. 
In  the  spring  following  the  budding,  the  stock  is  cut  off 
just  above  the  bud,  so  that  only  the  shoot  from  the  bud 
grows  to  make  the  future  tree.     This  prevailing  form  of 

budding  (shield-budding)  is   shown   in  Fig. 

168. 


Suggestions.  —  128.  Name  the  plants  that  the 
gardener  propagates  by  means  of  cuttings. 
129.  By  means  of  grafts.  130.  The  cutting-box 
may  be  set  in  the  window.  If  the  box  does  not 
receive  direct  sunlight,  it  may  be  covered  with  a 
pane  of  glass  to  prevent  evaporation.  Take  care 
that  the  air  is  not  kept  too  close,  else  the  damping- 
off  fungi  may  attack  the  cuttings,  and  they  will 
rot  at  the  surface  of  the  ground.  See  that  the 
pane  is  raised  a  little  at  one  end  to  afford  ventila- 
tion ;  and  if  the  water  collects  in  drops  on  the 
under  side  of  the  glass,  remove  the  pane  for  a 
time.  131.  Grafting  wax  is  made  of  beeswax, 
resin,  and  tallow.  A  good  recipe  is  one  part  (as 
one  pound)  of  rendered  tallow,  two  parts  of  bees- 
wax, four  parts  of  rosin  ;  melt  together  in  a  kettle  ; 
pour  the  liquid  into  a  pail  or  tub  of  water  to  so- 
lidify it ;  work  with  the  hands  until  it  has  the 
color  and  "grain"  of  taffy  candy,  the  hands  being 
greased  when  necessary.  The  wax  will  keep  any 
length  of  time.  For  the  little  grafting  that  any 
pupil  would  do,  it  is  better  to  buy  the  wax  of  a 
seedsman.  132.  Grafting  is  hardly  to  be  recom- 
mended as  a  general  school  diversion,  as  the  mak- 
ing of  cuttings  is  ;  and  the  account  of  it  in  this 
chapter  is  inserted  chief! v  to  satisfy  the  general 
curiosity  on  the  subject.  133.  In  Chap.  V  we  had 
a  definition  of  a  plant  generation  :  what  is  "  one 
generation  "  of  a  grafted  fruit  tree,  as  Le  Conte 
pear,  Baldwin,  or  Ben  Davis  apple?  134.  The 
Elberta  peach  originated  about  iSSo  :  what  is 
meant  by  "  originated  "  ?  135.  How  is  the  grape 
propagated  so  as  to  come  true  to  name  (explain 
what  is  meant  by  "coming  true")?  -currant? 
strawberry?  raspberry?  blackberry?  peach? 
pear?  orange?  fig?  plum?  cherry?  apple?  chest- 
nut? pecan? 


Fig.  i68.  —  Bud- 
ding. The 
"bud";  the 
opening  to  re- 
ceive it ;  the 
bud  tied. 


CHAPTER   XVII 

HOW   PLANTS   CLIMB 

We  have  found  that  plants  struggle  or  contend  for  a 
place  in  which  to  live.  Some  of  them  become  adapted  to 
grow  in  the  forest  shade,  others  to  grow  on  other  plants, 
as  epiphytes,  others  to  climb  to  the  light.  Observe  how 
woods  grapes,  and  other  forest  climbers,  spread  their  foli- 
age on  the  very  top  of  the  forest  tree,  while  their  long 
flexile  trunks  may  be  bare. 

There  are  several  ways  by  which  plants  climb,  but  most 
climbers  may  be  classified  into  four  groups  :  ( i )  scramblers, 
(2)  root  climbers,  (3)  tendril  climbers,  (4)  twiners. 

Scramblers. — Some  plants  rise  to  light  and  air  by  rest- 
ing their  long  and  weak  stems  on  the  tops  of  bushes  and 
quick-growing  herbs.  Their  stems  may  be  elevated  in  part 
by  the  growing  twigs  of  the  plants  on  which  they  recline. 
Such  plants  are  scramblers.  Usually  they  are  provided 
with  prickles  or  bristles.  In  most  weedy  swamp  thickets, 
scrambling  plants  may  be  found.  Briers,  some  roses,  bed- 
straw  or  galium,  bittersweet  {Solatium  Dulcamara,  not  the 
Celastrus),  the  tear-thumb  polygonums,  and  other  plants  are 
familiar  examples  of  scramblers. 

Root  Climbers.  —  Some  plants  climb  by  means  of  true 
roots.  These  roots  seek  the  dark  places  and  therefore 
enter  the  chinks  in  walls  and  bark.  The  trumpet  creeper 
is  a  familiar  example  (Fig.  36).  The  true  or  English 
ivy,  which  is  often  grown  to  cover  buildings,  is  another 
instance.  Still  another  is  the  poison  ivy.  Roots  are 
k  129 


130 


PLANT  BIOLOGY 


Fig.  169.  —  Tendril,  to  show 
where  the  coil  is  changed. 


distinguished    from    stem    tendrils    by    their    irregular  or 
indefinite  position  as  well  as  by  their  mode  of  growth. 

Tendril  climbers.  —  A  slender  coiling  part  that  serves  to 
hold  a  climbing  plant  to  a  support, is  known  as  a  tendril. 

The  free  end  swings  or  curves 
until  it  strikes  some  object,  when 
it  attaches  itself  and  then  coils 
and  draws  the  plant  close  to  the 
support.  The  spring  of  the  coil 
also  allows  the  plant  to  move  in 
the  wind,  thereby  enabling  the 
plant  to  maintain  its  hold.  Slowly  pull  a  well-matured 
tendril  from  its  support,  and  note  how  strongly  it  holds 
on.  Watch  the  tendrils  in  a  wind-storm.  Usually  the 
tendril  attaches  to  the  support  by  coiling  about  it,  but  the 
Virginia  creeper  and  Boston  ivy  (Fig.  170)  attach  to  walls 
by  means  of  disks 
on  the  ends  of  the 
tendrils. 

Since    both    ends 
of    the    tendril    are 
fixed,  when  it  finds 
a  support,  the  coil- 
ing  would    tend    to 
twist  it  in  two.      It 
will  be  found,  how- 
ever, that  the  tendril 
coils  in  different  di- 
rections in  different  parts  of  its  length 
ing  an  old  and  stretched-out  tendril,  the  change  of  direction 
in  the  coil  occurred  at  a.     In  long  tendrils  of  cucumbers 
and  melons  there  may  be  several  changes  of  direction. 
Tendrils  may  represent  either  branches  or  leaves.     In  the 


Fig.  170. — Tendril 
of  Boston  Ivy. 

In  Fig.  169,  show- 


HOW  PLANTS   CLIMB 


131 


Virginia  creeper  and  grape  they  are  branches  ;  they  stand 
opposite  the  leaves  in  the  position  of  fruit  clusters,  and 
sometimes  one  branch  of  a  fruit  cluster  is  a  tendril.  These 
tendrils  are  therefore  homologous  with  fruit-clusters,  and 
fruit-clusters  are  branches. 

In  some  plants  tendrils  are  leaflets  (Chap.  XI).  Ex- 
amples are  the  sweet  pea  and  common  garden  pea.  In 
Fig.  171,  observe  the  leaf  with  its  two  great 
stipules,  petiole,  six  normal  leaflets,  and  two 
or  three  pairs  of  leaflet  tendrils  and  a  termi- 
nal leaflet  tendril.  The  cobea,  a  common 
garden  climber,  has  a  similar  arrangement. 
In  some  cases  tendrils  are  stipules,  as  prob- 
ably in  the  green  briers 
(smilax). 

The  petiole  or  midrib 
may  act  as  a  tendril,  as 
in  various  kinds  of  clem- 
atis. In  Fig.  172,  the 
common  wild  clematis 
or  "old  man  vine,"  this 
mode  is  seen. 

Twiners.  —  The  entire 
plant  or  shoot  may  wind  about  a  support.  Such  a  plant  is 
a  twiner.  Examples  are  bean,  hop,  morning-glory,  moon- 
flower,  false  bittersweet  or  waxwork  (Celastrus),  some 
honeysuckles,  wistaria,  Dutchman's  pipe,  dodder.  The 
free  tip  of  the  twining  branch  sivceps  about  in  curves,  much 
as  the  tendril  does,  until  it  finds  support  or  becomes  old 
and  rigid. 

Each  kind  of  plant  usually  coils  in  only  one  direction. 
Most  plants  coil  against  the  sun,  or  from  the  observer's 
left  across   his  front  to  his  right  as  he  faces  the  plant. 


Fig.  171.  —  Leaves  of  Pea, 
—  very  large  stipules,  op- 
posite leaflets,  and  leaflets 
represented  by  tendrils. 


132 


PLANT  BIOLOGY 


Examples  are  bean,  morning-glory.     The  hop  twines  from 
the  observer's  right  to  his     A      left,  or  with  the  sun. 


Fig.  172. —Clematis  climbing  by  Leaf-tendril. 

Suggestions.  — 136.  Set  the  pupil  to  watch  the  behavior  of  any 
plant  that  has  tendrils  at  different  stages  of  maturity.  A  vigorous 
cucumber  plant  is  one  of  the  best.  Just  beyond  the  point  of  a  young 
straight  tendril  set  a  stake  to  compare  the  position  of  it.  Note 
whether  the  tendril  changes  position  from  hour  to  hour  or  day 
to  day.  137.  Is  the  tip  of  the  tendril  perfectly  straight?  Why? 
Set  a  small  stake  at  the  end  of  a  strong  straight  tendril,  so  the 
tendril  will  just  reach  it.  Watch,  and  make  drawing.  138.  If  a 
tendril  does  not  find  a  support,  what  does  it  do?  139.  To  test  the 
movement  of  a  free  tendril,  draw  an  ink  line  lengthwise  of  it,  and 
note  whether  the  line  remains  always  on  the  concave  side  or  the 
convex  side.  140.  Name  the  tendril-bearing  plants  that  you  know. 
141.  Make  similar  observations  and  experiments  on  the  tips  of 
twining  stems.  142.  What  twining  plants  do  you  know,  and  which 
way  do  they  twine  ?  143.  How  does  any  plant  that  you  know  get 
up  in  the  world?  144.  Does  the  stem  of  a  climbing  plant  con- 
tain more  or  less  substance  (weight)  than  an  erect  self-supporting 
stem  of  the  same  height  ?     Explain. 


CHAPTER   XVIII 

THE   FLOWER  — ITS   PARTS   AND   FORMS 

The  function  of  the  flower  is  to  produce  seed.  It  is 
probable  that  all  its  varied  forms  and  colors  contribute 
to  this  supreme  end.  These  forms  and  colors  please  the 
human  fancy  and  add  to  the  joy  of  living,  but  the  flower 
exists  for  the  good  of  the  plant,  not  for  the  good  of  man. 
The  parts  of  the  flower  are  of  two  general  kinds  —  those 
that  are  directly  concerned  in  the  production  of  seeds,  and 
those  that  act  as  covering  and  protecting  organs.  The 
former  parts  are  known  as  the  essential  organs;  the  latter 
as  the  floral  envelopes. 

Envelopes.  —  The  floral  envelopes  usually  bear  a  close 
resemblance  to  leaves.  These  envelopes  are  very  com- 
monly of  two  series  or  kinds  —  the 
outer  and  the  inner.  The  outer  series, 
known  as  the  calyx,  is  usually  smaller 
and  green.  It  usually  comprises  the 
outer  cover  of  the  flower  bud.  The 
calyx  is  the  lowest  whorl  in  Fig.  173.       FlG_  I73._  flower  of 

The    inner    series,    known    as    the       A  buttercup  in  sec- 
tion. 
corolla,  is    usually   colored   and   more 

special  or  irregular  in   shape   than   the  calyx.     It  is  the 

showy  part  of  the  flower,  as  a  rule.     The  corolla  is  the 

second  or  large  whorl  in  Fig.  173. 

The  calyx  may  be  composed  of  several  leaves.     Each 

leaf  is  a  sepal.     If  it  is  of  one  piece,  it  may  be  lobed  or 

divided,  in  which  case  the  divisions  are  called  calyx -lobes. 

»33 


134 


PLANT  BIOLOGY 


In  like  manner,  the  corolla  may  be  composed  of  petals,  or 
it  may  be  of  one  piece  and  variously  lobed.  A  calyx  of 
one  piece,  no  matter  how  deeply  lobed,  is  gamosepalous. 
A  corolla  of  one  piece  is  gamopetalous.  When  these 
series  are  of  separate  pieces,  as  in  Fig.  173,  the  flower  is 
said  to  be  polysepalous  and  polypetalous.     Sometimes  both 

series  are  of  separate  parts,  and 
sometimes  only  one  of  them  is  so 
formed. 

The  floral  envelopes  are  ho- 
mologous with  leaves.  Sepals  and 
petals,  at  least  when  more  than 
three  or  five,  are  in  more  than 
one  whorl,  and  one  whorl  stands 
below  another  so  that  the  parts 
overlap.  They  are  borne  on  the 
expanded  or  thickened  end  of  the 
flower  stalk  ;  this  end  is  the  torus. 
In  Fig.  173  all  the  parts  are  seen 
as  attached  to  the  torus.  This 
part  is  sometimes  called  the  re- 
ceptacle, but  this  word  is  a  common-language  term  of 
several  meanings,  whereas  torus  has  no  other  meaning. 
Sometimes  one  part  is  attached  to  another  part,  as  in  the 
fuchsia  (Fig.  174),  in  which  the  petals  are  borne  on  the 
calyx-tube. 

Subtending  Parts.  —  Sometimes  there  are  leaf-like  parts 
just  below  the  calyx,  looking  like  a  second  calyx.  Such 
parts  accompany  the  carnation  flower.  These  parts  are 
bracts  (bracts  are  small  specialized  leaves);  and  they  form 
an  involucre.  We  must  be  careful  that  we  do  not  mistake 
them  for  true  flower  parts.  Sometimes  the  bracts  are 
large  and  petal-like,  as  in  the  great  white  blooms  of  the 


Fig.  174.  —  Flower  of 
Fuchsia  in  Section. 


THE   FLOWER  — ITS  PARTS  AND   FORMS 


135 


flowering    dogwood :    here    the    real    flowers    are    several, 
small  and  greenish,  forming  a  small  cluster  in  the  center. 

Essential  Organs.  —  The  essential  organs  are  of  two 
series.  The  outer  series  is  composed  of  the  stamens.  The 
inner  series  is  composed  of  the  pistils. 

Stamens  bear  the  pollen,  which  is  made  up  of  grains  or 
spores,  each  spore  usually  being  a  single  plant  cell.  The 
stamen  is  of  two  parts,  as  is  readily  seen  in  Figs.  173, 
174,  —  the  enlarged  terminal  part  or  anther,  and  the  stalk 
or  filament.  The  filament  is  often  so  short  as  to  seem  to 
be  absent,  and  the  anther  is  then  said  to  be  sessile.  The 
anther  bears  the  pollen  spores.  It  is  made  up  of  two  or 
four  parts  (known  as  sporangia  or  spore-cases),  which 
burst  and  discharge  the 
pollen.  When  the  pollen  is 
shed,  the  stamen  dies. 

The  pistil  has  three 
parts :  the  lowest,  or  seed- 
bearing  part,  which  is  the 
ovary ;  the  stigma  at  the 
upper  extremity,  which  is 
a  flattened  or  expanded 
surface,  and  usually  rough- 
ened or  sticky  ;  the  stalk- 
like part  or  style,  connect- 
ing the  ovary  and  stigma. 
Sometimes  the  style  is  apparently  wanting,  and  the  stigma 
is  said  to  be  sessile  on  the  ovary.  These  parts  are  shown 
in  the  fuchsia  (Fig.  174).  The  ovary  or  seed  vessel  is  at  a. 
A  long  style,  bearing  a  large  stigma,  projects  from  the 
flower.     See  also  Figs.  175  and  176. 

Stamens  and  pistils  probably  are  homologous  with  leaves. 
A  pistil  is  sometimes  conceived  to  represent  anciently  a 


Fig.  175.  —  The  Structure  of  a 
Plum  Blossom. 

se,  sepals;  f,  petals:  sta,  stamens;  o,  ovary; 
j,  style;  st,  stigma.  The  pistil  consists  of 
the  ovary,  style,  and  stigma.  It  contains 
the  ^eed  part.  The  stamens  are  tipped  with 
anthers,  in  which  the  pollen  is  borne.  The 
ovary,  o,  ripens  into  the  fruit. 


136 


PLANT  BIOLOGY 


Fig.  176.  —  Simple 
Pistils  of  But- 
tercup, one  in 
longitudinal  sec- 
tion. 


leaf  as  if  rolled  into  a  tube  ;  and  an  anther,  a  leaf  of  which 
the  edges  may  have  been  turned  in  on  the  midrib. 

The  pistil  may  be  of  one  part  or  com- 
partment, or  of  many  parts.  The  different 
units  or  parts  of  which  it  is  composed  are 
carpels.  Each  carpel  is  homologous  with 
a  leaf.  Each  carpel  bears  one  or  more 
seeds.  A  pistil  of  one  carpel  is  simple ; 
of  two  or  more  carpels,  compound.  Usu- 
ally the  structure  of  the  pistil  may  be  de- 
termined by  cutting  horizontally  across  the  lower  or  seed- 
bearing  part,  as  Figs.  177,  178  explain.  A  flower  may 
contain  a  simple  pistil  (one  carpel),  as 
the  pea  (Fig.  177);  several  simple  pis- 
tils (several  separate  carpels),  as  the 
buttercup  (Fig.  176);  or  a  compound 
pistil  with  carpels  united,  as  the  Saint 
John's  wort  (Fig.  178)  and  apple.  How 
many  carpels  in  an  apple  ?  A  peach  ? 
An  okra  pod  ?  A  bean  pod  ?  The 
seed  cavity  in  each  carpel  is  called  a 
locule  (Latin  locus,  a  place).  In  these 
locules  the  seeds  are  borne. 

Conformation  of  the  Flower.  —  A 
flower  that  has  calyx,  corolla,  stamens, 
and  pistils  is  said  to  be  complete  (Fig. 
173);  all  others  are  incomplete.  In 
some  flowers  both  the  floral  envelopes 
are  wanting  :  such  are  naked.  When 
one  of  the  floral  envelope  series  is 
wanting,  the  remaining  series  is  said 
to  be  calyx,  and  the  flower  is  therefore 
apetalous  (without  petals).     The  knot- 


Fir,.  177.  —  Pistil  of 
Garden  Pea,  the 
stamens  being  pulled 
down  in  order  to  dis- 
close it;  also  a  section 
showing  the  single 
compartment  (com- 
pare Fig.  188). 


Fig.  178. —Compound 
Pistil  of  a  St. 
John's  Wort.  It 
has  5  carpels. 


THE  FLOWER  — ITS  PARTS  AND   FORMS 


137 


weed  (Fig.  179),  smartweed,  buckwheat,  elm  are 
examples. 

Some  flowers  lack  the  pistils  :  these  are  stami- 
nate,  whether  the  envelopes  are  missing  or  not. 
Others  lack  the  stamens :  these  are  pistillate. 
Others  have  neither  stamens  nor  pistils:  these 
are  sterile  (snowball  and  hydrangea).    Those 
that  have  both  stamens  and  pistils  are  per- 
fect, whether  or  not  the  envelopes  are  missing. 

Those  that  lack 

■  fV 


either  stamens  or 
pistils  are  imper- 
fect or  diclinous. 
Staminate  and 
pistillate  flowers 
are  imperfect  or 
diclinous. 
When  staminate  and  pistillate  flowers  are  borne  on  the 

same  plant,  e.g.   oak  (Fig.    180),  corn, 

beech,  chestnut,  hazel,  walnut,  hickory, 

pine,  begonia  (Fig.    181),   watermelon, 


Fig.  179.  —  Knotweed,  a  very  common  but  inconspicu- 
ous plant  along  hard  walks  and  roads.  Two  flowers, 
enlarged,  are  shown  at  the  right.  These  flowers  are 
very  small  and  borne  in  the  axils  of  the  leaves. 


Fig.  180.  — Staminate  Catkins  of 
Oak.  The  pistillate  flowers  are  in  the 
leaf  axils,  and  not  shown  in  this  pic- 
ture. 


Fig.  181.—  Begonia 
Flowers. 

Staminate  at  A ;  pistil- 
late below,  with  the 
winged  ovary  at  B. 


138 


PLANT  BIOLOGY 


gourd,  pumpkin,  the  plant  is  monoecious  ("in  one  house"). 

When  they  are  on  different  plants,  e.g.  poplar,  cottonwood, 

bois  d'arc,  willow  (Fig.  182), 
the  plant  is  dioecious  ("in  two 
houses  ").  Some  varieties  of 
strawberry,  grape,  and  mul- 
berry are  partly  dioecious.  Is 
the  rose  either  monoecious 
or  dioecious  ? 

Flowers  in  which  the  parts 
of  each  series  are  alike  are 
said  to  be  regular  (as  in  Figs. 
173,  174,  175).  Those  in 
which  some  parts  are  unlike 
other  parts  of  the  same  series 

are  irregular.      Their    regularity  may  be  in  calyx,  as  in 

nasturtium  (Fig.  183);  in  corolla  (Figs.  184,  185);  in  the 
stamens  (compare  nasturtium,  catnip, 
Fig.  185,  sage);  in  the  pistils.  Irregu- 
larity is  most  frequent  in  the  corolla. 


Fig.  182.  —  Catkins  of  a  Willow. 

A  staminate  flower  is  shown  at  s,  and  a 
pistillate  flower  at  /.  The  staminate 
and  pistillate  are  on  different  plants. 


Fig.  183.  —  Flower  of 
Garden  Nasturtium. 

Separate  petal  at  a.  The 
calyx  is  produced  into  a 
spur. 


Fig.  185.— 

Flower  of 

Catnip. 


Fig.  184. —  The  Five  Petals 
of  the  Pansy,  detached  to 
show  the  form. 


THE   FLOWER —  ITS  PARTS  AND   FORMS  139 

Various  Forms  of  Corolla.  —  The  corolla  often  assumes 
very  definite  or  distinct  forms,  especially  when  gamopet- 
alous.  It  may  have  a  long  tube  with  a  wide-flaring  limb, 
when  it  is  said  to  be  funnelforrn,  as  in  morning-glory 
and  pumpkin.  If  the  tube  is  very  narrow  and  the  limb 
stands  at  right  angles  to  it,  the  corolla  is  salverform,  as 
in  phlox.  If  the  tube  is  very  short  and  the  limb  wide- 
spreading  and  nearly  circular  in  outline,  the  corolla  is 
rotate  or  wheel-shaped,  as  in  potato. 

A  gamopetalous  corolla  or  gamosepalous  calyx  is  often 
cleft  in  such  way  as  to  make  two  prominent  parts.  Such 
parts  are  said  to  be  lipped  or  labiate.  Each  of  the  lips  or 
lobes  may  be  notched  or  toothed.  In  5-membered  flowers, 
the  lower  lip  is  usually  3-lobed  and  the  upper  one  2-lobed. 
Labiate  flowers  are  characteristic  of  the  mint  family  (Fig. 
185),  and  the  family  therefore  is  called  the  Labiate.  (Lit- 
erally, labiate  means  merely  "lipped,"  without  specifying  the 
number  of  lips  or  lobes ;  but  it  is  commonly  used  to  desig- 
nate 2-lipped  flowers.)  Strongly  2-parted  polypetalous 
flowers  may  be  said  to  be  labiate ;  but  the  term  is  often- 
est  used  for  gamopetalous  co- 
rollas. 

Labiate  gamopetalous  flowers 
that  are  closed  in  the  throat  (or 
entrance  to  the  tube)  are  said  to 
be  grinning  or  personate  (per- 
sonate means  masked,  or  person-      Fia  ^6. -Personate  Flower 

r  of  Toadflax. 

like).      Snap-dragon  is  a  typical 

example;  also  toadflax  or  butter-and-eggs  (Fig.  186),  and 
many  related  plants.  Personate  flowers  usually  have 
definite  relations  to  insect  pollination.  Observe  how  an 
insect  forces  his  head  into  the  closed  throat  of  the  toad- 
flax. 


140 


PLANT   BIOLOGY 


The  peculiar  flowers  of  the  pea  tribes  are  explained  in 
Figs.  187,  [88. 

Spathe  Flowers.  —  In  many  plants,  very  simple  (often 
naked)  flowers  are  borne  in  dense,  more  or  less  fleshy 
spikes,  and  the  spike  is  inclosed  in  or  attended  by  a  leaf, 
sometimes  corolla-like,  known  as  a  spathe.  The  spike  of 
flowers  is  technically  known  as  a  spadix.  This  type  of 
flower  is  characteristic  of  the  great  arum  family,  which  is 


Fig.  187.  —  Flowers  of  the 
Common  Bean,  with  one 
flower  opened  (a)  to  show 
the  structure. 


Fig.  188.— Diagram  of  Alfalfa  Flower 
in  Section  : 

C,  calyx,  D,  standard;  W,  wing;  A",  keel;  T,  sta- 
men-tube; F,  filament  of  tenth  stamen;  A", 
stigma;  Y,  style;  O,  ovary;  the  dotted  lines  at 
/."  show  position  of  stamen  tube,  when  pushed 
upward  by  insects.     Enlarged. 


chiefly  tropical.  The  commonest  wild  representatives  in 
the  North  are  Jack-in-the-pulpit,  or  Indian  turnip,  and 
skunk  cabbage.  In  the  former  the  flowers  are  all  diclin- 
ous and  naked.  In  the  skunk  cabbage  all  the  flowers  are 
perfect  and  have  four  sepals.  The  common  calla  is  a 
good  example  of  this  type  of  inflorescence. 

Compositous  Flowers.  —  The  head  (anthodium)  or  so- 
called  "flower"  of  sunflower  (Fig.  189),  thistle,  aster, 
dandelion,  daisy,  chrysanthemum,  goldenrod,  is  com- 
posed of  several  or  many  little  Jloivrrs,  or  florets.     These 


THE  FLOWER  — ITS  PARTS  AND  FORMS 


f4I 


Fig.  189.  — Head  of  Sunflower. 


At  b  is  a  much-divided 


florets  are  inclosed  in  a  more  or  less  dense  and  Usually 
green  involucre.  In  the  thistle  (Fig.  190)  this  involucre  is 
prickly.  A  longitudinal 
section  discloses  the  flo- 
rets, all  attached  at  bot- 
tom to  a  common  torus, 
and  densely  packed  in 
the  involucre.  The  pink 
tips  of  these  florets  con- 
stitute the  showy  part  of 
the  head. 

Each  floret  of  the  this- 
tle (Fig.   190)  is  a  com- 
plete flower.     At  a  is  the  ovary, 
plumy  calyx,  known  as  the  pappus.     The  corolla  is  long- 
tubed,  rising  above  the  pappus,  and  is  enlarged  and  5-lobed 

at  the  top,  c.  The  style  pro- 
jects at  e.  The  five  anthers 
are  united  about  the  style  in 
a  ring  at  d.  Such  anthers 
are  said  to  be  syngenesious. 
These  are  the  various  parts 
of  the  florets  of  the  Com- 
positae.  In  some  cases  the 
pappus  is  in  the  form  of 
barbs,  bristles,  or  scales,  and 
sometimes  it  is  wanting. 
The  pappus,  as  we  shall  see 
later,  assists  in  distributing 
the  seed.  Often  the  florets 
are  not  all  alike.  The  corolla 
of  those  in  the  outer  circles  may  be  developed  into  a  long, 
straplike,  or  tubular  part,  and  the  head  then  has  the  ap- 


Fig.  190.  —  Longitudinal  Section 
of  Thistle  Head;  also  a  Floret 
of  Thistle. 


i4: 


PL A. XT   BIOLOGY 


pearance  of  being  one  flower  with  a  border  of  petals.  Of 
such  is  the  sunflower  (Fig.  189),  aster,  bachelor's  button  or 
cornflower,  and  field  daisy  (Fig.  211).  These  long  corolla- 
limbs  are  called  rays.  In  some  cultivated  composites,  all 
the  florets  may  develop  rays,  as  in  the  dahlia  and  chrysan- 
themum. In  some  species,  as  dandelion,  all  the  florets 
naturally  have  rays.  Syngenesious  arrangement  of  an- 
thers is  the  most  characteristic  single  feature  of  the 
composites. 

Double  Flowers.  —  Under  the  stimulus  of  cultivation  and 
increased    food    supply,  flowers   tend    to    become    double. 

True  doubling  arises 
in  two  ways,  mor- 
phologically :  ( 1 ) sta- 
mens  or  pistils  may 
produce  petals  (Fig. 
191 )  ;  (2)  adventi- 
tious or  accessory 
petals  may  arise  in 
the  circle  of  petals. 
Both  of  these  cate- 
gories may  be  pres- 
ent in  the  same 
flower.  In  the  full 
double  hollyhock  the  petals  derived  from  the  staminal  col- 
umn are  shorter  and  make  a  rosette  in  'the  center  of  the 
flower.  In  Fig.  192  is  shown  the  doubling  of  a  daffodil 
by  the  modification  of  stamens.  Other  modifications  of 
flowers  are  sometimes  known  as  doubling.  For  example, 
double  dahlias,  chrysanthemums,  and  sunflowers  are  forms 
in  which  the  disk  flowers  have  developed  rays.  The  snow- 
ball is  another  case.  In  the  wild  snowball  the  external 
flowers  of  the  cluster  are  large  and  sterile.     In  the  culti- 


Fig.  191.  —  Petals  arising  from  the  Stami- 
nal Column  of  Hollyhock,  and  accessory 
petals  in  the  corolla-whorl. 


THE   FLOWER  — ITS  PARTS  AND   FORMS  1 43 

vated  plant  all  the  flowers  have  become  large  and  sterile. 
Hydrangea  is  a  similar  case. 


Fig.  192.  —  Narcissis  or  Daffodil.     Single  flower  at  the  right. 

Suggestions. — 145.  If  the  pupil  has  been  skillfully  conducted 
through  this  chapter  by  means  of  careful. study  of  specimens  rather 
than  as  a  mere  memorizing  process,  he  will  be  in  mood  to  chal- 
lenge any  flower  that  he  sees  and  to  make  an  effort  to  understand 
it.  Flowers  are  endlessly  modified  in  form ;  but  they  can  be 
understood  if  the  pupil  looks  first  for  the  anthers  and  ovaries. 
How  may  anthers  and  ovaries  always  be  distinguished?  146.  It  is 
excellent  practice  to  find  the  flowers  in  plants  that  are  commonly 
known  by  name,  and  to  determine  the  main  points  in  their  struc- 
ture. What  are  the  flowers  in  Indian  corn?  pumpkin  or  squash? 
celery?  cabbage?  potato?  pea?  tomato?  okra?  cotton?  rhubarb? 
chestnut?  wheat?  oats?  147.  Do  all  forest  trees  have  flowers? 
Explain.  148.  Name  all  the  monoecious  plants  you  know. 
Dioecious.  149.  What  plants  do  you  know  that  bloom  before 
the  leaves  appear?  Do  any  bloom  after  the  leaves  fall?  150.  Ex- 
plain the  flowers  of  marigold,  hyacinth,  lettuce,  clover,  asparagus, 
garden  calla,  aster,  locust,  onion,  burdock,  lily-of-the-valley,  crocus, 
Golden  Glow  rudbeckia,  cowpea.     151.    Define  a  flower. 

Note  to  the  Teacher.  —  It  cannot  be  urged  too  often  that 
the  specimens  themselves  be  studied.  If  this  chapter  becomes  a 
mere  recitation  on  names  and  definitions,  the  exercise  will  be 
worse  than  useless.  Properly  taught  by  means  of  the  flowers 
themselves,  the  names  become  merely  incidental  and  a  part  of 
the  pupil's  language,  and  the  subject  has  living  interest. 


CHAPTER   XIX 


THE  FLOWER  — FERTILIZATION  AND  POLLINATION 


Fertilization. — Seeds  result  from  the  union  of  two  ele- 
ments or  parts.     One  of  these  elements  is  a  cell-nucleus 

of  the  pollen-grain.  The  other  ele- 
ment is  the  cell-nucleus  of  an  egg- 
cell,  borne  in  the  ovary.  The 
pollen-grain  falls  on  the  stigma 
(Fig.  193).  It  absorbs  the  juices 
exuded  by  the  stigma,  and  grows 
by  sending  out  a  tube  (Fig.  194). 
This  tube  grows  downward  through 
the  style,  absorbing  food  as  it  goes, 
and  finally  reaches  the  egg-cell  in 
the  interior  of  an  ovule  in  the 
ovary  (Fig.  195),  and  fertilization, 
or  union  of  a  nucleus  of  the  pollen  and  the 
nucleus  of  the  egg-cell  in  the  ovule,  takes  place. 
The  ovule  and  embryo  within  then  develops 
into  a  seed.  The  growth  of  the  pollen-tube  is 
often  spoken  of  as  germination  of  the  pollen, 
but  it  is  not  germination  in  the  sense  in  which 
the  word  is  used  when  speaking  of  seeds. 

Better  seeds  —  that  is,  those  that  produce 
stronger  and  more  fruitful  plants  —  often  re- 
sult when  the  pollen  comes  from  another  flower. 
Fertilization  effected  between  different  flowers 

is  cross-fertilization ;   that  resulting  from  the 

144 


Fig.  193.  —  B,  Pollen  escap- 
ing from  anther;  A,  pollen 
germinating  on  a  stigma. 
Enlarged. 


Fig.  194.— 
A  Pollen- 
grain  and 
the  Grow- 
ing Tube. 


THE  FL O IV ER  —  FEE  11  LIZA  TION  AND  POLLINA  TION      1 4 5 


m 


application  of  pollen  to  pistils  in  the  same  flower  is  close- 
fertilization  or  self-fertilization.  It  will  be  seen  that  the 
cross-fertilization  relationship  may  be  of  many  degrees  — 
between  two  flowers  in  the  same  cluster,  between  those 
in  different  clusters  on  the  same 
branch,  between  those  on  different 
plants.  Usually  fertilization  takes 
place  only  between  plants  of  the 
same  species  or  kind. 

In  many  cases  there  is,  in  effect, 
an  apparent  selection  of  polloi  when 
pollen  from  two  or  more  sources  is 
applied  to  the  stigma.  Sometimes 
the  foreign  pollen,  if  from  the  same 
kind  of  plant,  grows,  and  fertiliza- 
tion results,  while  pollen  from  the 
same  flower  is  less  promptly  effec- 
tive. If,  however,  no  foreign  pol- 
len is  present,  the  pollen  from  the 
same  flower  may  finally  serve  the 
same  purpose. 

In  order  that  the  pollen  may  grow,  the  stigma  must  be 
ripe.  At  this  stage  the  stigma  is  usually  moist  and  some- 
times sticky.  A  ripe  stigma  is  said  to  be  receptive.  The 
stigma  may  remain  receptive  for  several  hours  or  even 
days,  depending  on  the  kind  of  plant,  the  weather,  and  how 
soon  pollen  is  received.  Watch  a  certain  flower  every  day 
to  see  the  anther  locules  open  and  the  stigma  ripen.  When 
fertilization  takes  place,  the  stigma  dies.  Observe,  also, 
how  soon  the  petals  wither  after  the  stigma  has  received 
pollen. 

Pollination. — The  transfer  of  the  pollen  from  anther 
to    stigma    is    known    as    pollination.      The    pollen    may 

L 


Fig.  195.  —  Diagram  to 
represent  fertiliza- 
TION. 

s,  stigma;  si,  style;  ov,  ovary;  o, 
ovule;  p,  pollen-grain;  pt, 
pollen-tube;  e,  egg-cell;  m, 
micropyle. 


146  PLANT  BIOLOGY 

fall  of  its  own  weight  on  the  adjacent  stigma,  or  it 
may  be  carried  from  flower  to  flower  by  wind,  insects,  or 
other  agents.  There  may  be  self-pollination  or  cross-pol- 
lination, and  of  course  it  must  always  precede  fertilization. 
m.  Usually  the  pollen  is  discharged  by  the  burst- 

(  \  ing  of  the  anthers.  The  commonest  method  of 
discharge  is  through  a  slit  on  either  side  of  the 
anther   (Fig.    193).       Sometimes    it    discharges 

through  a  pore  at  the  apex,  as  in   azalea  (Fig. 
Fig.  196.—  &  *  I  & 

anther  of    196),  rhododendron,    huckleberry,   wintergreen. 

Azalea,      jn  some  plants  a  part  of  the  anther  wall  raises 

opening  by 

terminal       or  falls  as  a  lid,  as  in  barberry  (Fig.  197),  blue 

pores.        cohosh,  May  apple.      The  opening  of  an  anther 

(as  also  of  a  seed-pod)  is  known  as  dehiscence  (dc,  from  ; 

hisco,  to  gape).     When  an  anther  or  seed  pod  opens,  it  is 

said  to  dehisce. 

Most  flowers  are  so  constructed  as  to  increase  the  chances 
of  cross-pollination.  We  have  seen  that  the  stigma  may 
have  the  power  of  choosing  foreign  pollen.  The 
commonest  means  of  necessitating  cross-pollina- 
tion is  the  different  times  of  maturing  of  stamens 
and  pistils  in  the  same  flower.  In  most  cases 
the  stamens  mature  first :  the  flower  is  then 
proterandrous.  When  the  pistils  mature  first, 
the  flower  is  proterogynous.  (A jut,  and/;  is  a 
Greek  root  often  used,  in  combinations,  for  sta-  barberry 
men,   and  gyne  for  pistil.)     The  difference  in       stamen, 

r      .  .  .  with  anther 

time  of  ripening  may  be  an  hour  or  two,  or  it  opening  by 
may  be  a  day.      The  ripening  of  the  stamens  lids- 

and  pistils  at  different  times  is  known  as  dichogamy,  and 
flowers  of  such  character  are  said  to  be  dichogamous. 
There  is  little  chance  for  dichogamous  flowers  to  pollinate 
themselves.     Many  flowers  are  imperfectly  dichogamous  — 


THE  EL  O  WER  —  FER  TILIZA  TION  AND  POLLINA  TION      1 47 


.  —  Flower  of  Hollyhock;  proterandrous. 


some  of  the  anthers  mature  simultaneously  with  the  pistils, 
so  that  there  is  chance  for  self-pollination  in  case  for- 
eign pollen  does 
not  arrive.  Even 
when  the  stigma 
receives  pollen 
from  its  own 
flower,  cross-fer- 
tilization may 
result.  The  hol- 
lyhock is  proter- 
androus. Fig. 
198  shows  a 
flower  recently 
expanded.  The  center  is  occupied  by  the  column  of  sta- 
mens. In  Fig.  199,  showing  an  older  flower,  the  long 
styles  are  conspicuous. 

Some  flozvcrs  arc  so  constructed  as  to  prohibit  self-polli- 
nation.    Very  irregular  flowers  are  usually  of  this  kind. 

With  some  of  them, 
the  petals  form  a 
sac  to  inclose  the 
anthers  and  the  pol- 
len cannot  be  shed 
on  the  stigma  but  is 
retained  until  a  bee 
forces  the  sac  open  ; 
the  pollen  is  rubbed 
on  the  hairs  of  the 
bee  and  transported. 
Regular  flowers  usu- 
ally depend  mostly  on  dichogamy  and  the  selective  powrer 
of    the   pistil   to   insure   crossing.      Flozvcrs  that  are  very 


Fig.  199.  — Older  Flower  of  Hollyhock. 


1 48 


PLANT  BIOLOGY 


irregular  and  provided  with  nectar  and  strong  perfume  arc 
n snail v  pollinated  by  insects.  Gaudy  colors  probably  attract 
insects  in  many  cases,  but  perfume  appears  to  be  a  greater 
attraction. 

The  insect  visits  the  flower  for  the 
nectar  (for  the  making  of  honey)  and 
may  unknowingly  carry  the  pollen. 
Spurs  and  sacs  in  the  flower  are  necta- 
ries (Fig.  200),  but  in  spurless  flowers 
the  nectar  is  usually  secreted  in  the 
bottom  of  the  flower  cnp.  This  compels 
the  insect  to  pass  by  the  anther  and 

fig.  200.—  flower  of    rub  against  the  pollen  before  it  reaches 
larkspur.  ^q  nectar.     Sometimes  the  anther  is  a 

long   lever   poised    on    the    middle    point    and    the    insect 

bumps  against  one  end  and  lifts 

it,  thus  bringing  the  other  end 

of  the  lever  with  the  pollen  sacs 

down  on  its  back.     Flowers  that 

are  pollinated  by  insects  are  said 

to  be  entomophilous  ("  insect  lov- 
ing"). Fig.  200  shows  a  larkspur. 

The  envelopes  are  separated  in 

Fig.  201.    The  long  spur  at  once 

suggests  insect  pollination.    The 

spur  is    a    sepal.      Two    hollow 

petals  project  into  this  spur,  ap- 
parently   serving   to    guide   the 

bee's  tongue.     The  two  smaller 

petals,  in    front,   are    peculiarly 

colored  and  perhaps  serve  the  bee  in  locating  the  nectary. 

The  stamens  ensheath  the  pistils  (Fig.  202).     As  the  insect 

stands  on  the  flower  and  thrusts  its  head  into  the  center, 


Fig.  201.  —  Envelopes  of  a 
Larkspur.  There  are  five 
wide  sepals,  the  upper  one  be- 
ing spurred.  There  are  four 
small  petals. 


THE  FLOWER— FERTILIZATION  A\D  TOLLLNATLON 


149 


the  envelopes  are  pushed  downward  and  outward  and 
the  pistil  and  stamens  come  in  contact  with  its  abdomen. 
Since  the  flower  is  proterandrous,  the 
pollen  that  the  pistils  receive  from  the 
bee's  abdomen  must  come  from  another 
flower.  Note  a  somewhat  similar  ar- 
rangement in  the  toadflax  or  butter-and- 
eggs. 

In  some  cases  (Fig.  203)  the  stamens 
are  longer  than  the  pistil  in  one  flower 
and  shorter  in  another.  If  the  insect 
visits  such  flowers,  it  gets  pollen  on  its 
head  from  the  long-stamen  flower,  and 
deposits  this  pollen  on  the  stigma  in  the 
long-pistil  flower.  Such  flowers  are  di- 
morphous (of  two  forms).  If  pollen  from  its  own  flower 
and  from  another  flower  both  fall  on  the  stigma,  the  proba- 
bilities are  that  the  stigma  will  choose  the  foreign  pollen. 


Fig.  202.  —  Stamens 
of  Larkspur,  sur- 
rounding the  pistils. 


Fig.  203. —  Dimorphic  Flowers  of  Primrose. 


Many  flozvers  are  pollinated  by  the  wind.      Thev  are  said 
to  be  anemophilous  ("  wind  loving  ").      Such  flowers  pro- 


150 


PLANT  BIOLOGY 


duce  great  quantities  of  pollen,  for  much  of  it  is  wasted. 
They  usually  have  broad  stigmas,  which  expose  large 
surfaces  to  the  wind.  They  are  usually  lacking  in  gaudy 
colors  and  in  perfume.  Grasses  and  pine  trees  are  typical 
examples  of  anemophilous  plants. 

In  many  cases  cross-pollination  is  insured  because  the 
stamens   and  pistils   are   in   different  flowers  (diclinous). 

Monoecious  and 
dioecious  plants 
may  be  polli- 
nated by  wind  or 
insects,  or  other 
agents  (Fig.  204). 
They  are  usually 
wind  -  pollinated, 
although  willows 
are  often,  if  not 
mostly,  insect- 
pollinated.  The 
Indian  corn  is  a 
monoecious  plant. 
M  The       staminate 

Fig.  204.  —  Flowers  of  Black  Walnut:  two  pis-      flowers    are    in    a 

tillate  flowers  at  A,  and  staminate  catkins  at  B. 

terminal  panicle 
(tassel).  The  pistillate  flowers  are  in  a  dense  spike  (ear), 
inclosed  in  a  sheath  or  husk.  Each  "  silk "  is  a  style. 
Each  pistillate  flower  produces  a  kernel  of  corn.  Some- 
times a  few  pistillate  flowers  are  borne  in  the  tassel  and  a 
few  staminate  flowers  on  the  tip  of  the  ear.  Is  self-fertili- 
zation possible  with  the  corn  ?  Why  does  a  "  volunteer  " 
stalk  standing  alone  in  a  garden  have  only  a  few  grains 
on  the  ear  ?  What  is  the  direction  of  the  prevailing  wind 
in    summer  ?     If    only    two    or    three    rows    of    corn    are 


\\\   1 1 

•  ■  ■  \  ■  V  \      v 


THE  FL  0 IV ER  —  PER  T I  LIZ  A  TION  AND  POLLINA  TION      I  5  I 


planted  in  a  garden  where  prevailing  winds  occur,  in  which 
direction  would  they  better  run  ? 

Although  most  flowers  are  of  such  character  as  to  insure 
or  increase  the  chances  of  cross-pollination,  there  are  some 
that  absolutely  forbid  crossing.  These  flowers  are  usually 
borne  beneath  or  on  the 
ground,  and  they  lack 
showy  colors  and  per- 
fumes. They  are  known 
as  cleistogamous  flowers 
(meaning  "  hidden  flow- 
ers"). The  plant  has 
normal  showy  flowers 
that  may  be  insect-pol- 
linated, and  in  addition 
is  provided  with  these 
simplified  flowers.  Only 
a  few  plants  bear  cleis- 
togamous flowers.  Hog- 
peanut,  common  blue 
violet,  fringed  winter- 
green,  and  dalibarda  are    Fig.  205.  — Common  Blue  Violet.     The 

.        .  .  .  ,  familiar   flowers   are   shown,   natural   size. 

the   best    Subjects    in   the  The  corolla  is  spurred.    Late  in  the  season, 

Northern     States.         Fi°".  cleistogamous  flowers   are  often  borne   on 

,  .    .  the  surface  of  the  ground.     A  small  one  is 

205     ShOWS    a    CleiStOga-  shown  at  a.     A  nearly  mature  pod  is  shown 

mous  flower  of  the  blue  at  b-  Both  a  and  b  are  one  ,hird  natural 
violet  at  a.     Above  the 

true  roots,  slender  stems  bear  these  flowers,  that  are 
provided  with  a  calyx,  and  a  curving  corolla  which  does 
not  open.  Inside  are  the  stamens  and  pistils.  Late  in 
the  season  the  cleistogamous  flowers  may  be  found  just 
underneath  the  mold.  They  never  rise  above  ground. 
The  following  summer  one  may  find  a  seedling  plant,  in 


1  ?2 


PLANT  BIOLOGY 


some  kinds  of  plants,  with  the  remains  of  the  old  cleistog- 
amous  flower  still  adhering  to  the  root.  Cleistogamous 
flowers    usually    appear    after    the    showy    flowers    have 


Fig.  206.  —  Pods  of  Peanuts  ripening  underground. 

passed.  They  seem  to  insure  a  crop  of  seed  by  a 
method  that  expends  little  of  the  plant's  energy.  The 
pupil  will  be  interested  to  work  out  the  fruiting  of  the  pea- 
nut (Fig.  206). 
Unbaked  fresh 
peanuts  grow 
readily  and  can 
easily  be  raised 
in  the  North  in 
a  warm  sandy 
garden. 

Suggestions.  — 
152.  Not  all  the 
flowers  produce 
seeds.  Note  that 
an  apple  tree  may 
bloom  very  full, 
but  that  only  rela- 
tively few  apples 
may  result  (Fig.  207).  More  pollen  is  produced  than  is  needed  to 
fertilize   the  flowers;    this  increases    the   chances   that    sufficient 


Fig.  207. — Struggle  for  Existence  among  the 
Apple  Flowers. 


THE  FL  O  WER  —  FEE  TILIZA  TION  AND  POLLINA  TION      I  5  3 

stigmas  will  receive  acceptable  pollen  to  enable  the  plant  to 
perpetuate  its  kind.  At  any  time  in  summer,  or  even  in  fall, 
examine  the  apple  trees  carefully  to  determine  whether  any  dead 
flowers  or  flower  stalks  still  remain  about  the  apple  ;  or,  examine 
any  full-blooming  plant  to  see  whether  any  of  the  flowers  fail. 
153.  Keep  watch  on  any  plant  to  see  whether  insects  visit  it. 
What  kind?  When?  What  for?  154.  Determine  whether  the 
calyx  serves  any  purpose  in  protecting  the  flower.  Very  carefully 
remove  the  calyx  from  a  bud  that  is  normally  exposed  to  heat 
and  sun  and  rain,  and  see  whether  the  flower  then  fares  as  well  as 
others.  155.  Cover  a  single  flower  on  its  plant  with  a  tiny  paper 
or  muslin  bag  so  tightly  that  no  insect  can  get  in.  If  the  flower 
sets  fruit,  what  do  you  conclude?  156.  Remove  carefully  the 
corolla  from  a  flower  nearly  ready  to  open,  preferably  one  that  has 
no  other  flowers  very  close  to  it.  Watch  for  insects.  157.  Find 
the  nectar  in  any  flower  that  you  study.  158.  Remove  the  stigma. 
What  happens?  159.  Which  of  the  following  plants  have  perfect 
flowers  :  pea,  bean,  pumpkin,  cotton,  clover,  buckwheat,  potato, 
Indian  corn,  peach,  chestnut,  hickory,  watermelon,  sunflower,  cab- 
bage, rose,  begonia,  geranium,  cucumber,  calla,  willow,  cotton- 
wood,  cantaloupe?  What  have  the  others?  160.  On  wind- 
pollinated  plants,  are  either  anthers  or  stigmas  more  numerous? 
161.  Are  very  small  colored  flowers  usually  borne  singly  or  in 
clusters  ?  162.  Why  do  rains  at  blooming  time  often  lessen 
the  fruit  crop  ?  163.  Of  what  value  are  bees  in  orchards  ? 
164.  The  crossing  of  plants  to  improve  varieties  or  to  obtain  new 
varieties.  —  It  may  be  desired  to  perform  the  operation  of  polli- 
nation by  hand.  In  order  to  insure  the  most  definite  results, 
every  effort  should  be  made  rightly  to  apply  the  pollen  which  it 
is  desired  shall  be  used,  and  rigidly  to  exclude  all  other  pollen. 
(a)  The  first  requisite  is  to  remove  the  anthers  from  the  flower 
which  it  is  proposed  to  cross,  and  they  must  be  removed  before  the 
pollen  has  been  shed.  The  flower-bud  is  therefore  opened  and  the 
anthers  taken  out.  Cut  off  the  floral  envelopes  with  small,  sharp- 
pointed  scissors,  then  cut  out  or  pull  out  the  anthers,  leaving  only 
the  pistil  untouched  ;  or  merely  open  the  corolla  at  the  end  and 
pull  out  the  anthers  with  a  hook  or  tweezers ;  and  this  method  is 
often  the  best  one.  It  is  best  to  delay  the  operation  as  long  as 
possible  and  yet  not  allow  the  bud  to  open  (and  thereby  expose 
the  flower  to  foreign  pollen)  nor  the  anthers  to  discharge  the 
pollen,  (b)  The  flower  must  next  be  covered  with  a  paper  bag  to 
prevent  the  access  of  pollen  (Figs.  208,  209).  If  the  stigma  is  not 
receptive  at  the  time  (as  it  usually  is  not),  the  desired  pollen  is 
not  applied  at  once.  The  bag  may  be  removed  from  time  to  time 
to  allow  of  examination  of  the  pistil,  and  when  the  stigma  is 
mature,  which  is  told  by  its  glutinous  or  roughened  appearance, 


154 


PLANT  BIOLOGY 


the  time  for  pollination  has  come.  If  the  bag  is  slightly  moist- 
ened, it  can  be  puckered  more  tightly  about  the  stem  of  the  plant. 
The  time  required  for  the  stigma  to  mature  varies  from  several 
hours  to  a  few  days.  (c)  When  the  stigma  is  ready,  an  unopened 
anther  from  the  desired  flower  is  crushed  on  the  finger  nail  or  a 
knife  blade,  and  the  pollen  is  rubbed  on  the  stigma  by  means  of  a 
tiny  brush,  the  point  of  a  knife  blade,  or  a  sliver  of  wood.     The 


Fig.  208.  — A  Paper  Bag, 
with  string  inserted. 


Fig.  209. —  The  Bag  tied 
over  a  Flower. 


flower  is  again  covered  with  the  bag,  which  is  allowed  to  remain 
for  several  days  until  all  danger  of  other  pollination  is  past.  Care 
must  be  taken  completely  to  cover  the  stigmatic  surface  with 
pollen,  if  possible.  The  seeds  produced  by  a  crossed  flower  pro- 
duce hybrids,  or  plants  having  parents  belonging  to  different 
varieties  or  species.  165.  One  of  the  means  of  securing  new 
forms  of  plants  is  by  making  hybrids.     Why  ? 


FlG.  2io.  —  Fig.    The  fig  is  a  hollow  torus  with  flowers  borne  on  the  inside, 
and  pollinated  by  insects  that  enter  at  the  apex. 


CHAPTER    XX 
FLOWER-CLUSTERS 


* 


have    seen   that 
Sometimes  the 


Origin    of    the    Flower-cluster.  —  We 

branches  arise  from  the  axils  of  leaves 
leaves  may  be  reduced  to  bracts 
and  yet  branches  are  borne  in 
their  axils.  Some  of  the  branches 
grow  into  long  limbs  ;  others  be- 
come short  spurs ;  others  bear 
Jlozuers.  In  fact,  a  flower  is  it- 
self a  specialized  branch. 

Flowers  are  usually  borne 
near  the  top  of  the  plant.  Often 
they  are  produced  in  great  num- 
bers. It  results,  therefore,  that 
flower  branches  usually  stand 
close  together,  forming  a  clus- 
ter. The  shape  and  arrange- 
ment of  the  flower-cluster  differ 
with  the  kind  of  plant,  since 
each  plant  has  its  own  mode  of 
branching. 

Certain  definite  or  well-marked 
types  of  flower-clusters  have  re- 
ceived names.  Some  of  these 
names  we  shall  discuss,  but  the 
flower-clusters  that  perfectly  match  the  definitions  are  the 
exception  rather  than  the  rule.     The  determining  of  the 

155 


Fig.  Mi.  —Terminal  Flowers 
of  THE  Whiteweed  (in  some 
places  called  ox-eye  daisy). 


i56 


PLANT  BIOLOGY 


kinds  of  flower-clusters  is  one  of  the  most  perplexing  sub- 
jects in  descriptive  botany.  We  may  classify  the  subject 
around  three  ideas  :  solitary  flowers,  centrifugal  or  deter- 
minate clusters,  centripetal  or  indeterminate  clusters. 

Solitary  Flowers.  —  In  many  cases  flowers  are  borne 
singly ;  they  are  separated  from  other  flowers  by  leaves. 
They  are  then  said  to  be  solitary.     The  solitary  flower  may 

be  cither  at  the  end  of  the 
main  shoot  or  axis  (Fig.  21 1  ), 
when  it  is  said  to  be  terminal ; 
or  from  the  side  of  the  shoot 
(Fig.  212),  when  it  is  said  to 
be  lateral  or  axillary. 

Centripetal  Clusters.  —  If 
the  flower-bearing  axils  were 
rather  close  together,  an  open 
or  leafy  flower-cluster  might 
result.  If  the  plant  continues 
to  grow  from  the  tip,  the 
older  flowers  are  left  farther 
and  farther  behind.  If  the 
cluster  were  so  short  as  to  be 
flat  or  convex  on  top,  the  out- 
ermost flowers  would  be  the 
older.  A  flower-cluster  in  which  the  lower  or  outer  flowers 
open  first  is  said  to  be  a  centripetal  cluster.  It  is  some- 
times said  to  be  an  indeterminate  cluster,  since  it  is  the 
result  of  a  type  of  growth  which  may  go  on  more  or  less 
continuously  from  the  apex. 

The  simplest  form  of  a  definite  centripetal  cluster  is  a 
raceme,  which  is  an  open  elongated  cluster  in  which  the 
flowers  are  borne  singly  on  very  short  branches  and  open 
from   below   (that   is,  from   the   older   part   of   the   shoot) 


Fig.  212.  —  Lateral  Flower  of 
AN  ABUTILON.  A  greenhouse 
plant. 


FL  O  WER-  CL  US  TERS 


157 


m 


upwards  (Fig.  213).     The  raceme  may  be  terminal  to  the 
main  branch;   or  it  may  be  lateral  to  it,  as  in   Fig.   214. 

Racemes  often  bear  the 
flowers  on  one  side  of 
the  stem,  thus  form- 
ic        inS  a  smgle  row- 
When  a  cen- 
tripetal flower- 
cluster  is  long 
and   dense   and 
the    flowers     are 
sessile   or  nearly  so, 
it   is    called   a    spike 
(Fig.  215).     Common 
examples    of     spikes 
are    plantain,   migno- 
nette,  mullein. 

A  very  short,  and 
dense  spike  is  a  head. 
Clover  (Fig.  216)  is 
a  good  example.  The 
sunflower  and  related 
plants  bear  many 
small  flowers  in  a 
very  dense  and  often  flat  head.  Note  that  in  the 
sunflower  (Fig.  189)  the  outside  or  exterior  flowers 

/ 


\\ 

Fig.  215.— 
Spike  of 
Plantain. 


Fig.  213.— Raceme  of  Currant. 
Terminal  or  lateral  ? 


Fig.  214.  — Lateral  Racemes  (in  fruit)  uk  Barberry. 


i58 


PLANT  BIOLOGY 


open  first.  Another  special  form  of  spike  is  the  catkin, 
which  usually  has  scaly  bracts,  the  whole  cluster  being 
deciduous  after  flowering  or  fruiting,  and  the  flowers  (in 
typical  cases)  having  only  stamens  or  pistils.      Examples 

are  the  "pussies"  of  willows  (Fig. 

182)  and  flower-clusters  of  oak  (Fig. 

180),  walnuts  (Fig.  204),  poplars. 


Fig.  216.  —  Head  of  Clo- 
ver Blossoms. 


Fig.  217.  — Corymb  of  Candy- 
tuft. 


When  a  loose,  elongated  centripetal  flower-cluster  has 
some  primary  branches  simple,  and  others  irregularly 
branched,  it  is  called  a  panicle.  It  is  a  branching  raceme. 
Because  of  the  earlier  growth  of  the  lower  branches,  the 
panicle  is  usually  broadest  at  the  base  or  conical  in  outline. 
True  panicles  are  not  very  common. 

When  an  indeterminate  flower-cluster  is  short,  so  that 


EL  O  WER-  CL  US  TEES 


159 


the  top  is  convex  or  flat,  it  is  a  corymb  (Fig.  217).  The 
outermost  flowers  open  first.  Centripetal  flower-clusters 
are  sometimes  said  to  be  corymbose  in  mode. 

When  the  branches  of  an  indeterminate  cluster  arise  from 
a  common  point,  like  the  frame  of  an  umbrella,  the  cluster 
is  an  umbel  (Fig.  218).  Typical  umbels  occur  in  carrot, 
parsnip,  caraway  and  other  plants  of  the  parsley  family  : 
the  family  is  known  as  the  Umbelliferae,  or  umbel-bearing 


Fig.  218.  —Remains  of  a  Last  Year's  Umbel  of  Wild  Carrot. 


family.  In  the  carrot  and  many  other  Umbelliferae,  there 
are  small  or  secondary  umbels,  called  umbellets,  at  the  end 
of  each  of  the  main  branches.  (In  the  center  of  the  wild 
carrot  umbel  one  often  finds  a  single,  blackish,  often 
aborted  flower,  comprising  a  i-flowered  umbellet.) 

Centrifugal  or  Determinate  Clusters.  —  When  the  ter- 
minal or  central  flower  opens  first,  the  cluster  is  said  to  be 
centrifugal.  The  growth  of  the  shoot  or  cluster  is  deter- 
minate, since  the  length  is  definitely  determined  or  stopped 
by  the  terminal  flower.  Fig.  219  shows  a  determinate  or 
centrifugal  mode  of  flower  bearing. 


i6o 


PLANT  BIOLOGY 


'-"V7^ 


Dense  centrifugal  clusters  are 
usually  flattish  on  top  because  of 
the  cessation  of  growth  in  the 
main  or  central  axis.  These  com- 
pact flower-clusters  are  known 
as  cymes.  Centrifugal  clusters 
are  sometimes  said  to  be  cymose 
in  mode.  Apples,  pears  (Fig. 
220),  and  elders  bear  flowers  in 
cymes.  Some  cyme-forms  are 
like  umbels  in  general  appear- 
ance. A  head-like  cymose  clus- 
ter is  a  glomerule  ;  it  blooms  from 
the  top  downwards  rather  than 
from  the  base  upwards. 

Mixed  Clusters.  —  Often  the 
cluster  is  mixed,  being  determi- 
nate in  one  part  and  indeterminate 
in  another  part  of  the  same  clus- 
ter. The  main  cluster  may  be  indeterminate,  but  the 
branches  determinate.  The  cluster  has  the  appearance  of 
a  panicle,  and  is  usually  so  called,  but  it  is  really  a  thyrse. 
Lilac  is  a  familiar  example  of  a 
thyrse.  In  some  cases  the  main 
cluster  is  determinate  and  the 
branches  are  indeterminate,  as  in 
hydrangea  and  elder. 

Inflorescence.  —  The  mode  or 
method  of  flower  arrangement  is 
known  as  the  inflorescence.  That 
is,  the  inflorescence  is  cymose,  co- 
rymbose, paniculate,  spicate,  solitary,  determinate,  inde- 
terminate.    By  custom,  however,  the  word  "  inflorescence  " 


Fig.  219.  —  Determinate  or 
Cymose  A R r.\ ngement.  — 

Wild  geranium. 


Fig.  220.  —  Cyme  of  Pear. 
Often  imperfect. 


FLOWER-CLUSTERS  l6l 


\ 


> 

* 

G 
>-• 

5 

/ 

5 

J' 

3 

/ 

1 

V 

3 

r 

^ 

Fig.  22i.  — Forms  of  Centripetal  Flower-clusters. 

i,  raceme;  2,  spike;   3,  umbel;  4,  head  or  anthodium;   5,  corymb. 


Fig.  222.  —  Centripetal  Inflorescence,  continued. 

6,  spadix;  7,  compound  umbel;  8,  catkin. 


Fig.  223.  — Centrifugal  Inflorescence. 

1,  cyme;  2,  scirpioid  raceme  (or  half  cyme). 


1 62  PLANT  BIOLOGY 

has  come  to  be  used  for  the  flower-cluster  itself  in  works 
on  descriptive  botany.  Thus  a  cyme  or  a  panicle  may  be 
called  an  inflorescence.  It  will  be  seen  that  even  solitary 
flowers  follow  either  indeterminate  or  determinate  methods 
of  branching. 

The  flower-stem.  —  The  stem  of  a  solitary  flower  is 
known  as  a  peduncle;  also  the  general  stem  of  a  flower- 
cluster.  The  stem  of  the  individual  flower  in  a  cluster  is 
a  pedicel.  In  the  so-called  stemless  plants  the  peduncle 
may  arise  directly. from  the  ground,  or  crown  of  the  plant, 
as  in  dandelion,  hyacinth,  garden  daisy ;  this  kind  of 
peduncle  is  called  a  scape.  A  scape  may  bear  one  or 
many  flowers.  It  has  no  foliage  leaves,  but  it  may  have 
bracts. 

Suggestions. — 166.  Name  six  columns  in  your  notebook  as 
follows  :  spike,  raceme,  corymb,  umbel,  cyme,  solitary.  Write 
each  of  the  following  in  its  appropriate  column  :  larkspur,  grape, 
rose,  wistaria,  onion,  bridal  wreath,  banana,  hydrangea,  phlox, 
China  berry,  lily-of-the-valley,  Spanish  dagger  (or  yucca),  sorghum, 
tuberose,  hyacinth,  mustard,  goldenrod,  peach,  hollyhock,  mul- 
lein, crepe  myrtle,  locust,  narcissus,  snapdragon,  peppergrass, 
shepherd's  purse,  coxcomb,  wheat,  hawthorn,  geranium,  carrot, 
elder,  millet,  dogwood,  castor  bean  ;  substitute  others  for  plants 
that  do  not  grow  in  your  region.  167.  In  the  study  of  flower- 
clusters,  it  is  well  to  choose  first  those  that  are  fairly  typical  of  the 
various  classes  discussed  in  the  preceding  paragraphs.  As  soon 
as  the  main  types  are  well  fixed  in  the  mind,  random  clusters 
should  be  examined,  for  the  pupil  must  never  receive  the  impres- 
sion that  all  flower-clusters  follow  the  definitions  in  books.  Clus- 
ters of  some  of  the  commonest  plants  are  very  puzzling,  but  the 
pupil  should  at  least  be  able  to  discover  whether  the  inflorescence 
is  determinate  or  indeterminate.  Figures  221  to  223  (from  the 
German)  illustrate  the  theoretical  modes  of  inflorescence.  The 
numerals  indicate  the  order  of  opening. 


CHAPTER  XXI 


FRUITS 


The  ripened  ovary,  with  its  attachments,  is  known  as  the 
fruit.  It  contains  the  seeds.  If  the  pistil  is  simple,  or  of 
one  carpel,  the  fruit 
also  will  have  one  com- 
partment. If  the  pistil 
is  compound,  or  of 
more  than  one  carpel, 
the  fruit  usually  has  an 
equal  number  of  com- 
partments. The  com- 
partments in  pistil  and 
fruit  are  known  as  lo- 
cules  (from  Latin  locus, 
meaning  "a  place"). 

The  simplest  kind 
of  fruit  is  a  ripened 
\-locnled  ovary.  The 
first  stage  in  complex- 
ity is  a  ripened  2-  or 
many-loaded  ovary.  Very  complex  forms  may  arise  by  the 
attachment  of  other  parts  to  the  ovary.  Sometimes  the  style 
persists  and  becomes  a  beak  (mustard  pods,  dentaria, 
Fig.  224),  or  a  tail  as  in  clematis;  or  the  calyx  may  be 
attached  to  the  ovary ;  or  the  ovary  may  be  embedded  in 
the  receptacle,  and  ovary  and  receptacle  together  consti- 
tute the  fruit :  or  an  involucre  may  become  a  part  of  the 

163 


Fig.  224.  — Dentaria,  or  Tooth-wort,  in 
fruit. 


1 64 


PLANT  BIOLOGY 


fruit,  as  possibly  in  the  walnut  and  hickory  (Fig.  225),  and 
cup  of  the  acorn  (Fig.  226).  The  chestnut  and  the  beech 
bear  a  prickly  involucre,  but  the  nuts,  ,    , 


Fig.   225.  —  Hickory-nut. 

The  nut  is  the  fruit,  con- 
tained in  a  husk. 


Fig.  226.  —  Live-oak  Acorn. 
The  fruit  is  the  "  seed  "  part ; 
the  involucre  is  the  "cup." 


or  true  fruits,  are  not  grown  fast  to  it,  and  the  involucre 
can  scarcely  be  called  a  part  of  the  fruit.  A  ripened  ovary 
is  a  pericarp.  A  pericarp  to  which  other  parts  adhere  has 
been  called  an  accessory  or  reenforced  fruit.  (Page  169.) 
Some  fruits  are  dehiscent,  or  split  open  at  maturity  and 
liberate  the  seeds ;  others  are  indehiscent,  or  do  not  open. 
A  dehiscent  pericarp  is  called  a  /  pod. 
The  parts  into  which  such 
a  pod  breaks  or  splits  are 
known  as  valves.  In  inde- 
hiscent fruits  the  seed  is 
liberated  by  the  decay  of 
the  envelope,  or  by  the 
rupturing  of  the  envelope 
by  the  germinating  seed. 
Indehiscent  winged  peri- 
carps are  known  as  samaras  or  key  fruits. 


Fig.  227.  —  Key  of 
Sugar  Maple. 


Fig.  228.  —  Key 

of  Common 
American  Elm. 


Maple  (Fig. 


227),  elm  (Fig.  228),  and  ash  (Fig.  93)  are  examples. 


FRUITS 


I65 


Fig.  229. — 
Akenes  of 
Buttercup. 


Fig.  230.  —  Akenes 
of  Buttercup, 
one  in  longitudi- 
nal section. 


Pericarps. — The  simplest  pericarp  is  a  dry,  one- 
seeded,  indehiscent  body.  It  is  known  as  an  akene.  A 
head  of  akenes  is  shown  in  Fig.  229,  and  the 
structure  is  explained  in  Fig. 
230.  Akenes  may  be  seen  in 
buttercup,  hepatica,  anemone, 
smartweed,  buckwheat. 

A  i-loculed  pericarp  which 
dehisces  along  the  front  edge 
(that  is,  the  inner  edge,  next 
the  center  of  the  flower)  is  a  follicle.  The. fruit  of  the 
larkspur  (Fig.  231)  is  a  follicle.  There  are  usually  five  of 
these  fruits  (sometimes  three  or 
four)  in  each  larkspur  flower,  each 
pistil  ripening  into  a  follicle.  If 
these  pistils  were  united,  a  single 
compound  pistil  would  be  formed. 
Columbine,  peony,  ninebark,  milk- 
weed, also  have  follicles. 

A    i-loculed    pericarp    that    de- 
hisces on  both  edges  is  a  legume. 
Peas  and  beans  are  typical  exara- 
232);  in  fact,  this  character  gives 
the    pea    family,  —  Leguminosae. 
Often  the    valves  of  the 
legume  twist  forcibly  and 
expel  the  seeds,  throwing 
them  some  distance.    The 
word  "pod"  is  sometimes  restricted  to 
legumes,  but  it  is  better  to  use  it  generi- 
cally  for  all  dehiscent  pericarps. 

A  compound   pod — dehiscing   peri- 
carp of  two  or  more  carpels  —  is  a  capsule  (Figs.  233,  234, 


pies  (Fig. 
name     to 


Fig.  232.  —  A 
Bean  Pod. 


Fig.  233.  —  Capsule  of 
Castor -oil  Bean- 
after  Dehiscence. 


1 66 


PLANT  BIOLOGY 


Fig.  234.  — Cap- 
sule of  Morn- 
ing Gloky. 


236,  237).  Some  capsules  are  of  one 
locule,  but  they  may  have  been  compound 
when  young  (in  the  ovary  stage)  and  the 
partitions  may  have  vanished.  Sometimes 
one  or  more  of  the  carpels  are  uniformly 
crowded  out  by  the  exclusive  growth  of 
other  carpels  (Fig.  235).  The  seeds  or 
parts  which  are  crowded  out  are  said  to 
be  aborted. 

There  are  several  ways  in  which  cap- 
sules dehisce  or  open.  When  they  break 
along  the  partitions  (or  septa),  the  mode  is  known  as  septi- 
cidal  dehiscence  (Fig.  236) ; 
In  septicidal  dehiscence  the 
fruit  separates  into  parts 
representing  the  original 
carpels.  These  carpels 
may  still  be  entire,  and 
they  then  dehisce  individu- 
ally, usually  along  the  inner 
edge  as  if  they  were  follicles.     When  the  compartments 

split  in  the  middle,  between  the 
partitions,  the  mode  is  loculicidal 
dehiscence  (Fig.  237).  In  some 
cases  the  dehiscence  is  at  the  top, 
when  it  is  said  to  be  apical  (al- 
though several  modes  of  dehis- 
cence are  here  included).  When 
the  ivJiole  top  comes  off,  as  in  purs- 
lane and  garden  portulaca  (Fig. 
238),  the  pod  is  known  as  a  pyxis.  In  some  cases  apical 
dehiscence  is  by  means  of  a  hole  or  clefts. 

The  peculiar  capsule  of  the  mustard   family,  or  Cruci 


Fig.  235.  —  Three-carpeled  Fruit 
of  Horse-chestnut.  Two  locules 
are  closing  by  abortion  of  the  ovules. 


Fig.  236.  — 
St.   John's 
Wort.  Sep- 
ticidal. 


Fig.  237.— 
Loculici- 
dal Pod  of 
Day-lily. 


FRUITS 


167 


feras,  is  known  as  a  silique  when  it  is  distinctly  longer  than 
broad  (Fig.  224),  and  a  silicle  when  its  breadth    nearly 


Fig.  238.  — Pyxis  of  Portu- 
laca  or  Rose-moss. 


Fig.  239. —  Berries  of  Goose- 
berry.    Remains  of  calyx  at  c. 


equals  or  exceeds  its  length.  A  cruciferous  capsule  is 
2-carpeled,  with  a  thin  partition,  each  locule  containing 
seeds  in  two  rows.  The  two  valves  detach  from  below 
Mp wards.     Cabbage,   turnip,  mustard,  water-cress,  radish, 

rape,  shepherd's  purse, 
sweet  alyssum,  wall- 
flower, honesty,  are 
examples. 


Fig.  240.—  Berry  of  the  Ground  Cherry 
or  Husk  Tomato,  contained  in  the  inflated 
calyx. 

The  pericarp  may  ho.  fleshy  and 
indehiscent.  A  pulpy  pericarp 
with  several  or  many  seeds  is  a 
berry  (Figs.  239,  240,  241).  To 
the  horticulturist  a  berry  is  a 
small,  soft,  edible   fruit,   without 


Fig.  241. —  Orange;  example 
of  a  berry. 


1 68 


PI  A. XT  BIOLOGY 


particular  reference  to  its  structure.  The  botanical  and 
horticultural  conceptions  of  a  berry  are,  therefore,  unlike. 
In  the  botanical  sense,  gooseberries,  currants,  grapes,  to- 
matoes, potato-balls,  and  even  eggplant  fruits  and  oranges 
(Fig.  241)  are  berries;  strawberries,  raspberries,  black- 
berries are  not. 

A  fleshy  pericarp  containing  one  relatively  large  seed 
or  stone  is  a  drupe.  Examples  are  plum  (Fig.  242),  peach, 
cherry,  apricot,  olive.  The  walls  of 
the  pit  in  the  plum,  peach,  and  cherry 
are  formed  from  the  inner  coats  of 
the  ovary,  and  the  flesh  from  the 
outer  coats.  Drupes  are  also  known 
as  stone-fruits. 

Fruits  that  are  formed  by  the  sub- 
sequent union  of  separate  pistils  are 
aggregate  fruits.  The  carpels  in 
aggregate  fruits  are  usually  more  or  less  fleshy.  In  the 
raspberry  and  blackberry  flower,  the  pistils  are  essentially 
distinct,  but  as  the 
pistils  ripen  they  co- 
here and  form  one 
body  (Figs.  243,  244). 


Fig.  242.  —  Plum  ;   exam- 
ple of  a  drupe. 


Fig.  244.  —  Aggregate 

Fruit  of  Mulberry; 

and  a  separate  fruit. 


Fig.  243.  — Fruit  of  Rasp- 
berry. 


Each  of  the  carpels  or  pistils  in  the 
raspberry  and  blackberry  is  a  little 
drupe,  or  drupelet.  In  the  rasp- 
berry the  entire  fruit  separates  from 
the  torus,  leaving  the  torus  on  the 
plant.     In  the  blackberry  and  dew- 


UNIVERSHT 

c  f 


FRUITS 


169 


berry  the  fruit  adheres  to  the  torus,  and  the  two  are  re- 
moved together  when  the  fruit  is  picked. 

Accessory  Fruits.  —  When  the  pericarp  and  some  other 
part  grow  together,  the  fruit  is  said  to  be  accessory  or 
reenforced.  An  example  is  the  straw- 
berry (Fig.  245).  The  edible  part  is  a 
greatly  enlarged  torus,  and  the  pericarps 
are  akenes  embedded  in  it.  These  akenes 
are  commonly  called  seeds. 

Various  kinds  of  reenforced  fruits  have 
received  special  names.  One  of  these  is 
the  hip,  characteristic  of  roses.  In  this 
case,  the  torus  is  deep  and  hollow,  like  an 
urn,  and  the  separate  akenes  are  borne 
inside  it.  The  mouth  of  the  receptacle 
may  close,  and  the  walls  sometimes  become  fleshy  ;  the 
fruit  may  then  be  mistaken  for  a  berry.  The  fruit  of  the 
pear,  apple,  and  quince  is  known  as  a 


Fig.  245.  —  Straw- 
berry; fleshy 

torus  in  which  akenes 
are  embedded. 


Fig.  246.  —  Section  of 
an  Apple. 


Fig.  247.  —  Cross-section 
of  an  Apple. 


pome.  In  this  case  the  five  united  carpels  are  completely 
buried  in  the  hollow  torus,  and  the  torus  makes  most  of 
the  edible  part  of  the  ripe  fruit,  while  the  pistils  are  repre- 
sented by  the  core  (Fig.  246).  Observe  the  sepals  on  the 
top  of  the  torus  (apex  of  the  fruit)  in  Fig.  246.  Note 
the  outlines  of  the  embedded  pericarp  in  Fig.  247. 


IJO  PLANT  BIOLOGY 

Gymnospermous  Fruits.  —  In  pine,  spruces,  and  their  kin, 
there  is  no  fruit  in  the  sense  in  which  the  word  is  used 
in  the  preceding  pages,  because  there  is  no  ovary.  The 
ovules  are  naked  or  uncovered,  in  the  axils  of  the  scales  of 
the  young  cone,  and  they  have  neither  style  nor  stigma. 
The  pollen  falls  directly  on  the  mouth  of  the  ovule.  The 
ovule  ripens  into  a  seed,  which  is  usually  winged.  Because 
the  ovule  is  not  borne  in  a  sac  or  ovary,  these  plants  are 
called  gymnosperms  (Greek  for  "naked  seeds").  All  the 
true  cone-bearing  plants  are  of  this  class ;  also  certain 
other  plants,  as  red  cedar,  juniper,  yew.  The  plants  are 
monoecious  or  sometimes  dioecious.  The  staminate  flowers 
are  mere  naked  stamens  borne  beneath  scales,  in  small 
yellow  catkins  which  soon  fall.  The  pistillate  flowers  are 
naked  ovules  beneath  scales  on  cones  that  persist  (Fig. 
29).     Gymnospermous  seeds  may  have  several  cotyledons. 

Suggestions.  — 168.  Study  the  following  fruits,  or  any  five  fruits 
chosen  by  the  teacher,  and  answer  the  questions  for  each  :  Apple, 
peach,  bean,  tomato,  pumpkin.  What  is  its  form  ?  Locate  the 
scar  left  by  the  stem.  By  what  kind  of  a  stem  was  it  attached  ? 
Is  there  any  remains  of  the  blossom  at  the  blossom  end  ?  De- 
scribe texture  and  color  of  surface.  Divide  the  fruit  into  the  seed 
vessel  and  the  surrounding  part.  Has  the  fruit  any  pulp  or  flesh? 
Is  it  within  or  without  the  seed  vessel?  Is  the  seed  vessel  simple 
or  subdivided?  What  is  the  number  of  seeds?  Are  the  seeds 
free,  attached  to  the  wall  of  the  vessel,  or  to  a  support  in  the 
center?  Are  they  arranged  in  any  order?  What  kind  of  wall  has 
the  seed  vessel?  What  is  the  difference  between  a  peach  stone 
and  a  peach  seed?  169.  The  nut  fruits  are  always  available  for 
study.  Note  the  points  suggested  above.  Determine  what  the 
meat  or  edible  part  represents,  whether  cotyledons  or  not.  Figure 
248  is  suggestive.  170.  Mention  all  the  fleshy  fruits  you  know, 
tell  where  they  come  from,  and  refer  them  to  their  proper  groups. 
171.  What  kinds  of  fruits  can  you  buy  in  the  market,  and  to  what 
groups  or  classes  do  they  belong?  Of  which  ones  are  the  seeds 
only,  and  not  the  pericarps,  eaten  ?  172.  An  ear  of  corn  is  always 
available  for  study.  What  is  it  —  a  fruit  or  a  collection  of  fruits  ? 
How  are  the  grains  arranged  on  the  cob  ?  How  many  rows  do 
you  count  on  each  of  several  ears  ?     Are  all  the  rows  on  an  ear 


FRUITS 


171 


equally  close  together  ?  Do  you  find  an  ear  with  an  odd  number 
of  rows  ?  How  do  the  parts  of  the  husk  overlap  ?  Does  the 
husk  serve  as  protection  from  rain  ?  Can  birds  pick  out  the  grains? 
How  do  insect  enemies  enter  the  ear  ?  How  and  when  do  weevils 
lay  eggs  on  corn  ?  173.  Study  a  grain  of  corn.  Is  it  a  seed  ? 
Describe  the  shape  of  a  grain.  Color.  Size.  Does  its  surface 
show  any  projections  or  depressions  ?  Is  the  seed-coat  thin  or 
thick  ?  Transparent  or  opaque  ?  Locate  the  hilum.  Where  is 
the  silk  scar  ?  What  is  the  silk  ?  Sketch  the  grain  from  the  two 
points  of  view  that  show  it  best.  Where  is  the  embryo  ?  Does 
the  grain  have  endosperm  ?  What  is  dent  corn  ?  Flint  corn  ? 
How  many  kinds  of  corn  do  you  know  ?     For  what  are  they  used  ? 


Fig.  248.  — Pecan 
Fruit. 


Note  to  Teacher.  —  There  are  few  more  interesting  subjects 
to  beginning  pupils  than  fruits,  —  the  pods  of  many  kinds,  forms, 
and  colors,  the  berries,  and  nuts.  This  interest  may  well  be 
utilized  to  make  the  teaching  alive.  All  common  edible  fruits 
of  orchard  and  vegetable  garden  should  be  brought  into  this  dis- 
cussion (some  of  the  kinds  are  explained  in  "  Lessons  with 
Plants").  Of  dry  fruits,  as  pods,  burs,  nuts,  collections  may  be 
made  for  the  school  museum.  Fully  mature  fruits  are  best  for 
study,  particularly  if  it  is  desired  to  see  dehiscence.  For  com- 
parison, pistils  and  partially  grown  fruits  should  be  had  at  the 
same  time.  If  the  fruits  are  not  ripe  enough  to  dehisce,  they 
may  be  placed  in  the  sun  to  dry.  In  the  school  it  is  well  to  have 
a  collection  of  fruits  for  study.  The  specimens  may  be  kept  in 
glass  jars.  Always  note  exterior  of  fruit  and  its  parts :  interior 
of  fruit  with  arrangement  and  attachment  of  contents. 


CHAPTER   XXII 


DISPERSAL   OF   SEEDS 


It  is  to  the  plant's  advantage  to  have  its  seeds  distributed 
as  widely  as  possible.  It  has  a  better  chance  of  surviving 
in  the  struggle  for  existence.  It  gets  away  from  competi- 
tion. Many  seeds  and  fruits  are  of  such  character  as  to 
increase  their  chances  of  wide  dispersal.  The  commonest 
means  of  dissemination  may  be  classed  under  four  heads  : 
/  explosive  fruits  ;  transportation  by  wind ;  transportation  by 


birds;  burs. 


Fig.  249.  —  Explosion  of 
the  Balsam  Pod. 


Fig.  250.  — Explosive 
Fruits  of  Oxalis. 

An  exploding  pod  is  shown 
at  c.  The  dehiscence  is 
shown  at  b.  The  structure 
of  the  pod  is  seen  at  a. 


Explosive  Fruits.  —  Some  pods  open  zvith  explosive  force 

■  and  discharge  the  seeds.     Even  bean  and  everlasting  peas 

'■  do  this.     More    marked    examples    are   the  locust,  witch 

hazel,  garden  balsam  (Fig.  249),  wild  jewel-weed  or  impa- 

tiens  (touch-me-not),  violet,  crane's-bill  or  wild  geranium, 

bull  nettle,  morning  glory,  and  the  oxalis  (Fig.  250).     The 

172 


DISPERSAL    OF  SEEDS  1 73 

oxalis  is  common  in  several  species  in  the  wild  and  in 
cultivation.  One  of  them  is  known  as  wood  sorrel.  Figure 
250  shows  the  common  yellow  oxalis.  The  pod  opens 
loculicidally.  The  elastic  tissue  suddenly  contracts  when 
dehiscence  takes  place,  and  the  seeds  are  thrown  violently. 
The  squirting  cucumber  is  easily  grown  in  a  garden  (pro- 
cure seeds  of  seedsmen),  and  the  fruits  discharge  the  seeds 
with  great  force,  throwing  them  many 
feet. 

Wind  Travelers. — Wind -transported 
seeds  are  of  two  general  kinds :  those 
that  are  provided  with  wings,  as  the  flat 
seeds  of  catalpa  (Fig.  251)  and  cone-bear- 
ing trees  and  the  samaras  of  ash,  elm, 
tulip-tree,  ailanthus,  and  maple ;  and 
those  which  have  feathery  buoys  or  para-  . 
chutes  to  enable  them  to  float  in  the  air. 
Of  the  latter  kind  are  the  fruits  of  many 
composites,  in  which  the  pappus  is 
copious  and  soft.  Dandelion  and  thistle  *-* 
are  examples.  The  silk  of  the  milkweed 
and  probably  the  hairs  on  the  cotton  seed 
have  a  similar  office,  and  also  the  wool  of 

the  cat-tail.     Recall  the  cottony  seeds  of!  fig.  251. —winged 

.,  .„  ,  ,  Seeds  of  Catalpa. 

the  willow  and  poplar. 

Dispersal    by   Birds.  —  Seeds   of  berries   and   of  other 

small  fleshy  fruits  are  carried  far  and  wide  by  birds.     The  ^ 

pulp  is  digested,  but  the  seeds  are  not  injured.     Note  how 

the   cherries,  raspberries,  blackberries,  June-berries,   and 

others  spring  up  in  the  fence  rows,  where  the  birds  rest. 

Some  berries  and  drupes  persist  far  into  winter,  when  they 

supply  food  to  cedar  birds,  robins,  and  the  winter  birds. 

Red   cedar  is  distributed  by  birds.     Many  of  these  pulpy 


174 


PLANT  BIOLOGY 


fruits  are  agreeable  as  human  food,  and  some  of  them 
have  been  greatly  enlarged  or  "  improved  "  by  the  arts  of 
the  cultivator.     The  seeds  are  usually  indigestible. 

Burs.  —  Many  seeds  and  fruits  bear  spines,  hooks,  and 
hairs,  which  adhere  to  the  coats  of  animals  and  to  clothing. 
The  burdock  has  an  involucre  with  hooked  scales,  contain- 
ing the  fruits  inside.  The  clotbur  is  also  an  involucre. 
Both  are  compositous  plants,  allied  to  thistles,  but  the 
whole  head,  rather  than  the  separate 
fruits,  is  transported.  In  some  com- 
positous fruits  the  pappus  takes  the 
form  of  hooks  and  spines,  as  in  the 
"  Spanish  bayonets  "  and  "  pitch- 
forks." Fruits  of  various  kinds  are 
known  as  "stick  tights,"  as  of  the 
agrimony  and  hound's-tongue.  Those 
who  walk  in  the  woods  in  late  sum- 
mer and  fall  are  aware 
that  plants  have  means 
of  disseminating  them- 
selves (Fig.  252).  If  it 
is  impossible  to  iden- 
tify the  burs  which  one 
finds  on  clothing,  the  seeds  may  be  planted  and  specimens 
of  the  plant  may  then  be  grown. 

Suggestions.  — 174.  What  advantage  is  it  to  the  plant  to  have 
,  its  seeds  widely  dispersed?  175.  What  are  the  leading  ways  in 
which  fruits  and  seeds  are  dispersed?  176.  Name  some  explosive 
fruits.  177.  Describe  wind  travelers.  178.  What  seeds  are  car- 
ried by  birds?  179.  Describe  some  bur  with  which  you  are 
familiar.  180.  Are  adhesive  fruits  usually  dehiscent  or  indehis- 
cent?  181.  Do  samaras  grow  on  low  or  tall  plants,  as  a  rule? 
182.  Are  the  cotton  fibers  on  the  seed  or  on  the  fruit?  183. 
Name  the  ways  in  which  the  common  weeds  of  your  region  are 
disseminated.     184.    This  lesson  will  suggest  other  ways  in  which 


Fig.  252.  —  Stealing  a  Ride. 


DISPERSAL    OF  SEEDS 


175 


seeds  are  transported.  Nuts  are  buried  by  squirrels  for  food ;  but 
if  they  are  not  eaten,  they  may  grow.  The  seeds  of  many  plants 
are  blown  on  the  snow.  The  old  stalks  of  weeds,  standing  through 
the  winter,  may  serve  to  disseminate  the  plant.  Seeds  are  carried 
by  water  down  the  streams  and  along  shores.  About  woolen  mills 
strange  plants  often  spring  up  from  seed  brought  in  the  fleeces. 
Sometimes  the  entire  plant  is  rolled  for  miles  before  the  winds. 
Such  plants  are  "  tumbleweeds."  Examples  are  Russian  thistle, 
hair  grass  or  tumblegrass  (Panicum  capillare),  cyclone  plant 
i  Cycloloma  platyphyllum),  and  white  amaranth  (Amarantus 
albus).  About  seaports  strange  plants  are  often  found,  having 
been  introduced  in  the  earth  that  is  used  in  ships  for  ballast. 
These  plants  are  usually  known  as  "  ballast  plants."  Most  of  them 
do  not  persist  long.  185.  Plants  are  able  to  spread  themselves  by 
means  of  the  great  numbers  of  seeds  that  they  produce.  How 
many  seeds  may  a  given  elm  tree  or  apple  tree  or  raspberry  bush 
produce? 


Fig.  253.  —  The    Fruits 
of  the  Cat-tail  are 

LOOSENED        BY       WlND 

and  Weather. 


CHAPTER    XXIII 


PHENOGAMS  AND  CRYPTOGAMS 


Fig.  254.  —  Christmas  Fern. 
—  Dryopteris  acrostichoides ; 
known  also  as  Aspidium. 


The  plants  thus  far  studied  produce  flowers;  and  the 

flowers  produce  seeds  by  means  of  which  the  plant  is  prop- 
agated.    There  are  other  plants, 
"N.       e^     h    Mfo  however,  that  produce  no  seeds, 

and  these  plants  (including  bac- 
teria) are  probably  more  numer- 
ous than  the  seed-bearing  plants. 
These  plants  propagate  by  means 
of  spores,  which  are  generative  cells, 
usually  simple,  containing  no  em- 
bryo. These  spores  are  very  small, 
and  sometimes  are  not  visible  to 
the  naked  eye. 
Prominent  among  the  spore- 
propagated  plants  are  ferns.     The 

common  Christmas  fern  (so  called 

because  it  remains  green    during 

winter)  is  shown  in  Fig.  254.    The 

plant  has  no  trunk.     The  leaves 

spring  directly  from  the  ground. 

The    leaves    of    ferns    are    called 

fronds.     They   vary    in   shape,   as 

other    leaves    do.     Some    of    the 

fronds  in  Fig.  254  are  seen  to  be 

narrower  at  the  top.     If  these  are 

examined  more  closely  (Fig.  255), 


Fig.  255.  —  Fruiting  Frond 
of  Christmas  Fern. 

Sori  at  a.    One  sorus  with  its  in- 
dusium  at  b. 


I76 


PHEN OGAMS  AND    CRYPTOGAMS 


177 


it  will  be  seen  that  the  leaflets  are  contracted  and  are 
densely  covered  beneath  with  brown  bodies.  These  bodies 
are  collections  of  sporangia  or  spore-cases. 


Fig. 


256.  —  Common  Polypode  Fern. 
Polypodium  vulgare. 


Fig.  257.  — Sori  and  Spo- 
rangium of  Polypode. 
A  chain  of  cells  lies  along 
the  top  of  the  sporangium, 
which  springs  back  elasti- 
cally  on  drying,  thus  dis- 
seminating the  spores. 


Fig.  258.  —  The  Brake 
Fruits  underneath 
the  Revolute 
Edges  of  the  Leaf. 


The  sporangia  are  collected  into  little  groups,  known  as 
sori  (singular,  sorus)  or  fruit-dots.  Each  sorus  is  covered 
with  a  thin  scale  or  shield,  known  as 
an  indusium.  This  indusium  sepa- 
rates from  the  frond  at  its  edges,  and 
the  sporangia  are  exposed.  Not  all 
ferns  have  indusia.  The  polypode 
(Figs.  256,  257)  does  not;  the  sori 
are  naked.     In  the  brake  (Fig.  258) 

and  maidenhair  (Fig.  259)  the 
edge  of  the  frond  turns  over 
and  forms  an  indusium.  The 
nephrolepis  or  sword  fern  of 
greenhouses  is  allied  to  the 
polypode.  The  sori  are  in  a 
single  row  on  either  side  the 
midrib  (Fig.  260).  The  indu- 
sium is  circular  or  kidney- 
Fig.  259.  —  Fritting  Pinnules  j 

of  Maidenhair  Fern.  shaped  and  open  at  one  edge 


178 


PLANT  BIOLOGY 


Fig.   260.  —  Part   of    Frond    of 
Sword  Fern.    To  the  pupil:  Is 

this  illustration  right  side  up  ? 


or  finally  all  around.  The 
Boston  fern,  Washington  fern, 
Pierson  fern,  and  others,  are 
horticultural  forms  of  the 
common  sword  fern.  In  some 
ferns  (Fig.  261)  an  entire 
frond  becomes  contracted  to 
cover  the  sporangia. 
The  sporangium  or  spore-case  of  a  fern  is  a  more  or  less 
globular  body  and  usually  with  a  stalk  (Fig.  257).  It  con- 
tains the  spores.  When  ripe  it 
bursts  and  the  spores  are  set  free. 
In  a  moist,  warm  place  the  spores 
germinate.  They  produce  a  small, 
flat,  thin,  green,  more  or  less  heart- 
shaped  membrane  (Fig.  262).  This 
is  the  prothallus.  Sometimes  the 
prothallus  is  an  inch  or  more 
across,  but  oftener  it  is'  less  than 
a  dime  in  size.  Although  easily 
seen,  it  is  commonly  unknown  ex- 
cept to  botanists.  Prothalli  may 
often  be  found  in  greenhouses  where  ferns   are  grown. 

Look  on  the  moist  stone  or 
brick  walls,  or  on  the  firm  soil 
of  undisturbed  pots  and  beds ; 
or  spores  may  be  sown  in  a 
damp,  warm  place. 

On   the    under   side  of   the 
prothallus  two  kinds  of  organs 

are     borne.     These     are     the 
Fig.  262.  —  Prothallus  of  a  ,  .  ,  .    . 

fern.    Enlarged.  archegonium   (containing    egg- 

Archegonia  at  a  ■,  antheridia  at  b.        cells)  and  the  antheridium  (con- 


Fig.  261.  -Fertile  and 

Sterile  Fronds  of  the 

Sensitive  Fern. 


■PHENOGAMS  AND    CRYPTOGAMS  179 

taining  sperm-cells).  These  organs  are  minute  specialized 
parts  of  the  prothallus.  Their  positions  on  a  particular 
prothallus  are  shown  at  a  and  b  in  Fig.  262,  but  in  some 
ferns  they  are  on  separate  prothalli  (plant  dioecious).  The 
sperm-cells  escape  from  the  antheridium  and  in  the  water 
that  collects  on  the  prothallus  are  carried  to  the  archegonium, 
where  fertilization  of  the  egg  takes  place.  From  the  ferti- 
lized egg-cell  a  plant  grows,  becoming  a  "fern."  In 
most  cases  the  prothallus  soon  dies.  The  prothallus  is  the 
gametophyte  (from  Greek,  signifying  the  fertilized  plant). 

The  fern  plant,  arising  from  the  fertilized  egg  in  the 
archegonium,  becomes  a  perennial  plant,  each  year  pro- 
ducing spores  from  its  fronds  (called  the  sporophyte)  ;  but 
these  spores —  which  are  merely  detached  special  kinds  of 
cells  —  produce  the  prothallic  phase  of  the  fern  plant, 
from  which  new  individuals  arise.  A  fern  is  fertilized  but 
once  i?i  its  lifetime.  The  "  fern "  bears  the  spore,  the 
spore  gives  rise  to  the  prothallus,  and  the  egg-cell  of  the 
prothallus  (when  fertilized)  gives  rise  to  the  fern. 

A  similar  alternation  of  generations  runs  all  through  the 
vegetable  kingdom,  although  there  are  some  groups  of 
plants  in  which  it  is  very  obscure  or  apparently  wanting. 
It  is  very  marked  in  ferns  and  mosses.  In  algas  (includ- 
ing the  seaweeds)  the  gametophyte  is  the  "  plant,"  as 
the  non-botanist  knows  it,  and  the  sporophyte  is  incon- 
spicuous. There  is  a  general  tendency,  in  the  evolution  of 
the  vegetable  kingdom,  for  the  gametophyte  to  lose  its  rela- 
tive importance  and  for  the  sporophyte  to  become  larger  and 
more  highly  developed.  In  the  seed-bearing  plants  the 
sporophyte  generation  is  the  only  one  seen  by  the  non- 
botanist.  The  gametophyte  stage  is  of  short  duration  and 
the  parts  are  small ;  it  is  confined  to  the  time  of  fertiliza- 
tion. 


180  PLANT  BIOLOGY 

The  sporophyte  of  seed  plants,  or  the  "plant"  as  we 
know  it,  produces  two  kinds  of  spores  —  one  kind  becom- 
ing pollen- grains  and  the  other  kind  embryo-sacs.  The 
pollen-spores  are  borne  in  sporangia,  which  are  united  into 
what  are  called  anthers.  The  embryo-sac,  which  contains 
the  egg-cell,  is  borne  in  a  sporangium  known  as  an  ovule. 
A  gametopliytic  stage  is  present  in  both  pollen  and  embryo 
sac :  fertilization  takes  place,  and  a  sporopliyte  arises.  Soon 
this  sporophyte  becomes  dormant,  and  is  then  known  as  an 
embryo.  The  embryo  is  packed  away  within  tight-fitting 
coats,  and  the  entire  body  is  the  seed.  When  the  condi- 
tions are  right  the  seed  grows,  and  the  sporophyte  grows 
into  herb,  bush,  or  tree.  The  utility  of  the  alternation  of 
generations  is  not  understood. 

The  spores  of  ferns  are  borne  on  leaves ;  the  spores  of 
seed-bearing  plants  are  also  borne  amongst  a  mass  of 
specially  developed  conspicuous  leaves  known  as  flowers, 
therefore  these  plants  have  been  known  as  the  flowering 
plants.  Some  of  the  leaves  are  developed  as  envelopes 
(calyx,  corolla),  and  others  as  spore-bearing  parts,  or  spo- 
rophylls  (stamens,  pistils).  But  the  spores  of  the  lower 
plants,  as  of  ferns  and  mosses,  may  also  be  borne  in  spe- 
cially developed  foliage,  so  that  the  line  of  demarcation 
between  flowering  plants  and  flowerless  plants  is  not  so 
definite  as  was  once  supposed.  The  one  definite  distinction 
between  these  two  classes  of  plants  is  the  fact  that  one  class 
produces  seeds  and  the  other  does  not.  The  seed-plants  are 
now  often  called  spermaphytes,  but  there  is  no  single 
coordinate  term  to  set  off  those  which  do  not  bear  seeds. 
It  is  quite  as  well,  for  popular  purposes,  to  use  the  terms 
phenogams  for  the  seed-bearing  plants  and  cryptogams  for 
the  others.  These  terms  have  been  objected  to  in  recent 
years  because  their  etymology  does  not  express  literal  facts 


PHENOGAMS  AND    CRYPTOGAMS 


181 


{phenogam    signifying    "showy    flowers,"    and    cryptogam 

"hidden  flowers"),  but  the  terms  represent  distinct  ideas 

in    classification.     The    cryptogams    include    three    great 

series  of  plants  —  the  Thallophytes  or  algae,  lichens,  and 

fungi;  the  Bryophytes  or  mosslike  plants;  the  Pteridophytes 

or  fernlike  plants. 

Suggestions.  — 186.    The  parts  of  a  fern  leaf     The  primary 
complete  divisions  of  a  frond  are  called  pinnae,  no  matter  whether 
the  frond  is  pinnate  or  not.      In 
ferns  the  word  "pinna"  is  used  in 
essentially  the  same  way  that  leaf- 
let is  in  the  once-compound  leaves 
of  other   plants.     The  secondary 
leaflets  are  called  pinnules,  and  in 
thrice,  or  more,  compound  fronds, 
the  last  complete  parts  or  leaflets 
are  ultimate  pinnules.     The  dia- 
gram (Fig.  263)  will  aid  in  making 
the    subject   clear.     If  the  frond 
were  not  divided  to  the  midrib,  it 
would  be  simple,  but  this  diagram 
represents    a    compound    frond. 
The  general  outline  of  the  frond, 
as  bounded  by  the  dotted  line,  is 
ovate.     The   stipe  is  very  short. 
The  midrib  of  a  compound  frond 
is  known  as  the  rachis.     In  a  de- 
compound frond,  this  main  rachis 
is  called  the  primary  rachis.    Seg- 
ments (not  divided  to  the  rachis) 
are  seen  at  the  tip,  and  down  to 
h  on  one  side  and  to  m  on  the 
other.     Pinnae  are  shown  at  i,  k,  I,  0,  n.     The  pinna  0  is  entire  ; 
n  is  crenate-dentate ;  i  is  sinuate  or  wavy,  with  an  auricle  at  the 
base  ;  k  and  /are  compound.     The  pinna  k  has  twelve  entire  pin- 
nules.    (Is  there  ever  an  even  number  of  pinnules  on  any  pinna?) 
Pinna  /  has  nine  compound  pinnules,  each  bearing  several  entire 
ultimate  pinnules.      The  spores.  — 187.    Lay  a  mature  fruiting  frond 
of  any  fern  on  white  paper,  top  side  up,  and  allow  it  to  remain  in 
a   dry,  warm    place.      The  spores  will  discharge  on  the  paper. 
188.    Lay  the  full-grown  (but   not   dry)   cap   of  a   mushroom   or 
toadstool  bottom  down  on  a  sheet  of  clean  paper,  under  a  venti- 
lated box  in  a  warm,  dry  place.     A  day  later  raise  the  cap. 


Fig.  263.  — Diagram  to  explain 
the  Terminology  of  the 
Frond. 


CHAPTER   XXIV 


STUDIES   IN    CRYPTOGAMS 


The  pupil  who  has  acquired  skill  in  the  use  of  the  com- 
pound microscope  may  desire  to  make  more  extended  ex- 
cursions into  the  cryptogamous  orders.  The  following 
plants  have  been  chosen  as  examples  in  various  groups. 
Ferns  are  sufficiently  discussed  in  the  preceding  chapter. 

Bacteria 

If  an  infusion  of  ordinary  hay  is  made  in  water  and  allowed  to 
stand,  it  becomes  turbid  or  cloudy  after  a  few  days,  and  a  drop 
under  the  microscope  will  show  the  presence  of  minute  oblong 
cells  swimming  in  the  water  perhaps  by  means  of  numerous  hair- 
like appendages,  that  project  through  the  cell  wall  from  the  pro- 
toplasm within.  At  the  surface  of  the  dish  containing  the  infusion 
the  cells  are  non-motile  and  are  united  in  long  chains.  Each 
of   these    cells    or    organisms    is    a   bacterium  (plural,  bacterid). 

(Fig-   1 35-) 

Bacteria  are  very  minute  organisms,  —  the  smallest  Known, — 
consisting  either  of  separate  oblong  or  spherical  cells,  or  of 
chains,  plates,  or  groups  of  such  cells,  depending  on  the  kind. 
They  possess  a  membrane-like  wall  which,  unlike  the  cell  walls  of 
higher  plants,  contains  nitrogen.  The  presence  of  a  nucleus  has 
not  been  definitely  demonstrated.  Multiplication  is  by  the  fission 
of  the  vegetative  cells  ;  but  under  certain  conditions  of  drought, 
cold,  or  exhaustion  of  the  nutrient  medium,  the  protoplasm  of  the 
ordinary  cells  may  become  invested  with  a  thick  wall,  thus  form- 
ing an  endospore  which  is  very  resistant  to  extremes  of  environ- 
ment.    No  sexual  reproduction  is  known. 

Bacteria  are  very  widely  distributed  as  parasites  and  sapro- 
phytes in  almost  all  conceivable  places.  Decay  is  largely  caused 
by  bacteria,  accompanied  in  animal  tissue  by  the  liberation  of 
foul-smelling  gases.  Certain  species  grow  in  the  reservoirs  and 
pipes  of  water  supplies,  rendering  the  water  brackish  and  often 
undrinkable.  Some  kinds  of  fermentation  (the  breaking  down  or 
decomposing  of  organic  compounds,  usually  accompanied  by  the 

182 


STUDIES  IN   CRYPTOGAMS  183 

formation  of  gas)  are  due  to  these  organisms.  Other  bacteria 
oxidize  alcohol  to  acetic  acid,  and  produce  lactic  acid  in  milk  and 
butyric  acid  in  butter.  Bacteria  live  in  the  mouth,  stomach,  in- 
testines, and  on  the  surface  of  the  skin  of  animals.  Some  secrete 
gelatinous  sheaths  around  themselves  ;  others  secrete  sulfur  or 
iron,  giving  the  substratum  a  vivid  color. 

Were  it  not  for  bacteria,  man  could  not  live  on  the  earth,  for 
not  only  are  they  agents  in  the  process  of  decay,  but  they  are 
concerned  in  certain  healthful  processes  of  plants  and  animals. 
We  have  learned  in  Chap.  VIII  how  bacteria  are  related  to  nitro- 
gen-gathering. 

Bacteria  are  of  economic  importance  not  alone  because  of  their 
effect  on  materials  used  by  man,  but  also  because  of  the  disease- 
producing  power  of  certain  species.  Pus  is  caused  by  a  spherical 
form,  tetanus  or  lock-jaw  by  a  rod-shaped  form,  diphtheria  by 
short  oblong  chains,  tuberculosis  or  "  consumption  "  by  more  slen- 
der oblong  chains,  and  typhoid  fever,  cholera,  and  other  diseases 
by  other  forms.  Many  diseases  of  animals  and  plants  are 
caused  by  bacteria.  Disease-producing  bacteria  are  said  to  be 
pathogenic. 

The  ability  to  grow  in  other  nutrient  substances  than  the  natu- 
ral one  has  greatly  facilitated  the  study  of  these  minute  forms 
of  life.  By  the  use  of  suitable  culture  media  and  proper  precau- 
tions, pure  cultures  of  a  particular  disease-producing  bacterium 
may  be  obtained  with  which  further  experiments  may  be  con- 
ducted. 

Milk  provides  an  excellent  collecting  place  for  bacteria  coming 
from  the  air,  from  the  coat  of  the  cow  and  from  the  milker.  Dis- 
ease germs  are  sometimes  carried  in  milk.  If  a  drop  of  milk  is 
spread  on  a  culture  medium  (as  agar),  and  provided  with  proper 
temperature,  the  bacteria  will  multiply,  each  one  forming  a  colony 
visible  to  the  naked  eye.  In  this  way,  the  number  of  bacteria 
originally  contained  in  the  milk  may  be  counted. 

Bacteria  are  disseminated  in  water,  as  the  germ  of  typhoid  fever 
and  cholera ;  in  milk  and  other  fluids ;  in  the  air ;  and  on  the 
bodies  of  flies,  feet  of  birds,  and  otherwise. 

Bacteria  are  thought  by  many  to  have  descended  from  algae  by 
the  loss  of  chlorophyll  and  decrease  in  size  due  to  the  more 
specialized  acquired  saprophytic  and  parasitic  habit. 

The  alga;  comprise  most  of  the  green  floating  "  scum  "  which 
covers  the  surfaces  of  ponds  and  other  quiet  waters.  The  masses 
of  plants  are  often  called  "  frog  spittle."  Others  are  attached  to 
stones,  pieces  of  wood,  and  other  objects  submerged  in  streams 


[84 


PLANT  BIOLOGY 


and  lakes,  and  many  are  found  on  moist  ground  and  on  dripping 
rocks.  Aside  from  these,  all  the  plants  commonly  known  as  seaweeds 
belong  to  this  category  ;  these  latter  are  inhabitants  of  salt  water. 
The  simplest  forms  of  algae  consist  of  a  single  spherical  cell, 
which  multiplies  by  repeated  division  or  fission.  Many  of  the 
forms  found  in  fresh  water  are  filamentous,  i.e.  the  plant  body 
consists  of  long  threads,  either  simple  or  branched.  Such  a  plant 
body  is  termed  a  thallus.  This  term  applies  to  the  vegetative 
body  of  all  plants  that  are  not  differentiated  into  stem  and  leaves. 
Such  plants  are  known  as  thallophytes  (p.  181).  All  algae  contain 
chlorophyll,  and  are  able  to  assimilate  carbon  dioxid  from  the  air. 
This  distinguishes  them  from  the  fungi. 

Nostoc.  — On  wet  rocks  and  damp  soil  dark,  semitransparent 
irregular  or  spherical  gelatinous  masses  about  the  size  of  a  pea  are 
often  found.  These  consist  of  a  colony  of  contorted  filamentous 
algae  embedded  in  the  jelly-like  mass.  The  chain  of  cells  in  the 
filament  is  necklace-like.  Each  cell  is  homogeneous,  without 
apparent  nucleus,  and  blue-green  in  color,  except  one  cell  which 
is  larger  and  clearer  than  the  rest.  The  plant  therefore  belongs 
to  the  group  of  blue-green  alga.  The  jelly  probably  serves  to 
maintain  a  more  even  moisture  and  to  provide  mechanical  protec- 
tion. Multiplication  is  wholly  by  the  breaking 
up  of  the  threads.  Occasionally  certain  cells 
of  the  filament  thicken  to  become  resting- 
spores,  but  no  other  spore  formation  occurs. 

Oscillatoria.  — The  blue-green  coatings 
found  on  damp  soil  and  in  water  frequently 
show  under  the  microscope  the  presence  of 
filamentous    algae    composed    of   many  short 


Fig. 


264. — Filament  of  Osciixatoria,  showing  one 
dead  cell  where  the  strand  will  break. 


homogeneous  cells  (Fig.  264).  If  watched 
closely,  some  filaments  will  be  seen  to  wave 
back  and  forth  slowly,  showing  a  peculiar  power 
of  movement  characteristic  of  this  plant. 
Multiplication  is  by  the  breaking  up  of  the 
threads.     There  is  no  true  spore  formation. 

Spirogyra.  —  One  of  the  most  common  forms 
of  the  green  algae  is  spirogyra  (Fig.  265).     This 


Fig.  265.  — Strand 
of  Spirogyra, 
showing  the  chlo- 
rophyll bands. 
There  is  a  nu- 
cleus at  a.  How 
many  cells,  or 
parts  of  cells,  are 
shown  in  this  fig- 
ure ? 


STUDIES  IN  CRYPTOGAMS 


I85 


plant  often  forms  the  greater  part  of  the  floating  green  mass  (or 

"  frog  spittle  ")  on  ponds.    The  threadlike  character  of  the  thallus 

can  be  seen  with  the  naked  eye  or  with  a  hand 

lens,   but   to   study  it  carefully   a   microscope 

magnifying    two    hundred    diameters    or   more 

must  be  used.     The  thread  is  divided  into  long 

cells  by  cross    walls    which,   according   to    the 

species,  are  either  straight  or  curiously  folded 

(Fig.    266).     The   chlorophyll    is    arranged    in 

beautiful  spiral  bands  near  the  wall  of  each  cell. 

From  the  character  of  these  bands  the   plant 

takes  its  name.     Each  cell  is  provided  with  a 

nucleus  and  other  protoplasm.     The  nucleus  is 

suspended  near  the  center  of  the  cell  (a,  Fig. 

265)  by  delicate  strands  of  protoplasm  radiat- 
ing toward  the  wall  and  terminating  at  certain 

points  in  the  chlorophyll  band.    The  remainder 

of  the  protoplasm  forms  a  thin  layer  lining  the 

wall.     The    interior   of    the   cell   is   filled    with 

cell-sap.     The  protoplasm  and  nucleus  cannot 

be  easily  seen,  but  if  the  plant  is  stained  with 

a  dilute  alcoholic  solution  of  eosin  they  become 

clear. 

Spirogyra  is  propagated  vegetatively  by  the 

breaking  off  of  parts  of  the  threads,  which  con- 
tinue to  grow  as  new  plants.     Resting-spores, 

which  may  remain  dormant  for  a  time,  are  formed  by  a  process 
known  as  conjugation.  Two  threads  lying  side 
by  side  send  out  short  projections,  usually  from 
ail  the  cells  of  a  long  series  (Fig.  266).  The 
projections  or  processes  from  opposite  cells 
grow  toward  each  other,  meet,  and  fuse,  form- 
ing a  connecting  tube  between  the  cells.  The 
protoplasm,  nucleus,  and  chlorophyll  band  of 
one  cell  now  pass  through  this  tube,  and  unite 
with  the  contents  of  the  other  cell.  The  en- 
tire mass  then  becomes  surrounded  by  a  thick 
cellulose  wall,  thus  completing  the  resting- 
spore,  or  zygospore  (z,  Fig.  266). 


Fig.  266.  —  Con- 
jugation of 
Spirogyra. 
Ripe  zygospores 
on  the  left ;  a, 
connecting 
tubes. 


Fig.  267.  — Strand, 
or  Filament  of 
Zygnema,  freed 
from  its  gelatinous 
covering. 


Zygnema  is  an  alga  closely  related  to  spiro- 
gyra and  found  in  similar  places.  Its  life 
history  is  practically  the  same,  but  it  differs 
from  spirogyra  in  having  two  star-shaped 
chlorophyll  bodies  (Fig.  267)  in  each  cell,  in- 
stead of  a  chlorophyll-bearing  spiral  band. 


1 86  PLANT  BIOLOGY 

I  'aucheria  is  another  alga  common  in  shallow  water  and  on 
damp  soil.  The  thallus  is  much  branched,  but  the  threads  are 
not  divided  by  cross  walls  as  in  spirogyra.  The  plants  are  attached 
by  means  of  colorless  root-like  organs  which  are  much  like  the 
rool  hairs  of  the  higher  plants  :  these  are  rhizoids.  The  chloro- 
phyll is  in  the  form  of  grains  scattered  through  the  thread. 

Vaucheria  has  a  special  mode  of  asexual  reproduction  by 
means  of  swimming  spores  or  swarm-spores.  These  are  formed 
singly  in  a  short  enlarged  lateral  branch  known  as  the  sporangium. 
When  the  sporangium  bursts,  the  entire  contents  escape,  forming 
a  single  large  swarm-spore,  which  swims  about  by  means  of 
numerous  lashes  or  cilia  on  its  surface.  The  swarm  spores  are  so 
large  that  they  can  be  seen  with  the  naked  eye.  After  swimming 
about  for  some  time  they  come  to  rest  and  germinate,  producing 
a  new  plant. 

The  formation  of  resting-spores  of  vaucheria  is  acomplished  by 
means   of  special  organs,  oogonia   (o,  Fig.   268)    and   antheridia 

(a,  Fig.  268).  Both  of 
these  are  specially  devel- 
oped branches  from  the 
thallus.  The  antheridia 
are  nearly  cylindrical,  and 
curved  toward  the  oogonia. 

„  „     ,_       ~  ,.  The  upper  part  of  an  an- 

tic. 268.  —  Thread  of  Vaucheria  with      .      .  ..rr     . r  „  , 

Oogonia  and  Antheridia.  thendium   is  cut  off  by  a 

cross  wall,  and  within  it 
numerous  ciliated  sperm -cells  are  formed.  These  escape  by  the 
ruptured  apex  of  the  antheridium.  The  oogonia  are  more  en- 
larged than  the  antheridia,  and  have  a  beak-like  projection  turned 
a  little  to  one  side  of  the  apex.  They  are  separated  from  the 
thallus  thread  by  a  cross  wall,  and  contain  a  single  large  green 
cell,  the  egg-cell.  The  apex  of  the  oogonium  is  dissolved,  and 
through  the  opening  the  sperm-cells  enter.  Fertilization  is  thus 
accomplished.  After  fertilization  the  egg-cell  becomes  invested 
with  a  thick  wall  and  is  thus  converted  into  a  resting-spore,  the 
oospore. 

Fucus.  —  These  are  rather  large  specialized  algae  belonging  to  the 
group  known  as  brown  seaweeds  and  found  attached  by  a  disk  to 
the  rocks  of  the  seashore  just  below  high  tide  (Fig.  269).  They 
are  firm  and  strong  to  resist  wave  action  and  are  so  attached  as  to 
avoid  being  washed  ashore.  They  are  very  abundant  algae.  In 
shape  the  plants  are  long,  branched,  and  multicellular,  with  either 
flat  or  terete  branches.  They  are  olive-brown.  Propagation  is  by 
the  breaking  off  of  the  branches.  No  zoospores  are  produced, 
as  in  many  other  seaweeds  ;  and  reproduction   is  wholly  sexual. 


STUDIES  IN   CRYPTOGAMS 


l87 


The  antheridia,  bearing  sperm-cells,  and  the  o'ogonia,  each  bearing 
eight  egg-cells,  are  sunken  in  pits  or  conceptades.  These  pits 
are  aggregated  in  the  swollen  lighter  colored  tips  of  some  of  the 
branches  (s,  s,  Fig.  269).  The  egg-cells  and  sperm-cells  escape 
from  the  pits  and  fertilization  takes  place  in  the  water.  The 
matured  eggs,  or  spores,  reproduce  the  fucus  plant  directly. 


Fig.  269.  —  Fucus.  Fruiting 
branches  at  s,  s.  On  the 
stem  are  two  air-bladders. 


Fig.  270.  —  Nitella. 


Nitella.  —  This  is  a  large  branched  and  specialized  fresh-water 
alga  found  in  tufts  attached  to  the  bottom  in  shallow  ponds  (Fig. 
270).  Between  the  whorls  of  branches  are  long  internodes  consisting 
of  a  single  cylindrical  cell,  which  is  one  of  the  largest  cells  known  in 
vegetable  tissue.  Under  the  microscope  the  walls  of  this  cell  are 
found  to  be  lined  with  a  layer  of  small  stationary  chloroplastids, 
within  which  layer  the  protoplasm,  under  favorable  circumstances, 
will  be  found  in  motion,  moving  up  one  side  and  down  the  other 
(in  rotation).  Note  the  clear  streak  up  the  side  of  the  cell  and  its 
relation  to  the  moving  current. 


Fungi 

Some  forms  of  fungi  are  familiar  to  every  one.  Mushrooms 
and  toadstools,  with  their  varied  forms  and  colors,  are  common 
in  fields,  woods,  and  pastures.  In  every  household  the  common 
molds  are  familiar  intruders,  appearing  on  old  bread,  vegetables, 
and  even  within  tightly  sealed  fruit  jars,  where  they  form  a  felt- 
like layer  dusted  over  with  blue,  yellow,  or  black  powder.  The 
strange  occurrence  of  these   plants  long   mystified    people,    who 


iSS 


PLANT   BIOLOGY 


thought  they  were  productions  of  the  dead  matter  upon  which  they 
grew,  but  now  we  know  that  a  mold,  as  any  other  plant,  cannot 
originate  spontaneously  ;  it  must  start  from  something  which  is 
analogous  to  a  seed.  The  "seed  "  in  this  case  is  a  spore.  A  spore 
in  iv  be  produced  by  a  vegetative  process  (growing  out  from  the 
ordinary  plant  tissues),  or  it  may  be  the  result  of  a  fertilization 
process. 

Favorable  conditions  for  the  growth  of  f/ngi.  —  Place   a  piece 

z    of  bread  under  a  moist  bell  jar  and    another    in    an    uncovered 

place  near  by.     Sow  mold  on  each.     Note  the  result  from  day  to 

day.     Moisten  a  third  piece  of  bread  with  weak  copper  sulfate 

(blue   vitriol)   or  mercuric  chlorid  solution, 

sow  mold,  cover  with  bell  jar,  note  results, 

and  explain.    Expose  pieces  of  different  kinds 

of  food  in  a  damp  atmosphere  and  observe 

the  variety  of  organisms  appearing.     Fungi 

are  saprophytes  or  parasites,  and  must  be 

^-^s&fM&^fi^     provided   with   organic   matter  on  which  to 

grow.     They  are  usually  most  abundant  in 

moist  places  and  wet  seasons. 

Fig.  271.  — Mucor  Mold.  —  One  of  these  molds  {Mucor   mu- 

mucedo, showing  habit,  cedo),  which  is  very  common  on  all  decay- 
ing fruits  and  vegetables,  is  shown  in  Fig. 
271,  somewhat  magnified.  When  fruiting,  this  mold  appears  as  a 
dense  mass  of  long  white  hairs,  often  over  an  inch  high,  standing 
erect  from  the  fruit  or  vegetable  on  which  it  is  growing. 

The    life  of  this   mucor  begins   with  a  minute  rounded  spore 
(a,  Fig.  272),  which  lodges  on  the  decaying  material.     When  the 
spore  germinates,  it  sends  out  a  delicate  thread  that  grows  rapidly 
in  length  and  forms  very  many  branches  that 
soon  permeate  every  part  of  the  substance  on 
which  the  plant  grows  (6,  Fig.  272).     One  of 
these   threads   is   termed   a   hypha.      All   the 
threads   together   form   the    mycelium    of  the 
fungus.      The  mycelium  disorganizes  the  ma- 
terial in  which  it  grows,  and  thus  the  mucor 
plant  (Fig.  271)  is  nourished.     It  corresponds 
physiologically  to  the  roots  and  stems  of  other 
plants. 

When  the  mycelium  is  about  two  days  old,  it  begins  to  form  the 
long  fruiting  stalks  which  we  first  noticed.  To  study  them,  use  a 
compound  microscope  magnifying  about  two  hundred  diameters. 
One  of  the  stalks,  magnified,  is  shown  in  a,  Fig.  274.  It  consists 
of  a  rounded    head,  the  sporangium,  sp,  supported  on  a    long, 


Fig.  272.  —  Spokes 
OFMucor,  some 
germinating. 


STUDIES  IN  CRYPTOGAMS 


189 


Fig.  274 


a,  sporangium;   b,  sporangium 
bursting;   c.  columella. 


delicate  stalk,  the  sporangiophore.  The  stalk  is  separated  from 
the  sporangium  by  a  wall  which  is  formed  at  the  base  of  the  spo- 
rangium. This  wall,  however,  does  not 
extend  straight  across  the  thread,  but  it 
arches  up  into  the  sporangium  like  an 
inverted  pear.  It  is  known  as  the  col- 
umella, c.  When  the  sporangium  is 
placed  in  water,  the  wall  immediately 
dissolves  and  allows  hundreds  of  spores, 
which  were  formed  in  the  cavity  within 
the  sporangium,  to  escape,  b.  All  that 
is  left  of  the  fruit  is  the  stalk,  with  the 
pear-shaped  columella  at  its  summit,  c. 
The  spores  that  have  been  set  free  by  the 
breaking  of  the  sporangium  wall  are  now 
scattered  by  the  wind  and  other  agents. 
Those  that  lodge  in  favorable  places  be- 
gin to  grow  immediately  and  reproduce 
the  fungus.     The  others  soon  perish. 

The  mucor  may  continue  to  reproduce  itself  in  this  way  indefi- 
nitely, but  these  spores  are  very  delicate  and 
usually  die  if  they  do  not  fall  on  favorable 
ground,  so  that  the  fungus  is  provided  with 
another  means  of  carrying  itself  over  unfavora- 
ble seasons,  as  winter.  This  is  accomplished 
by  means  of  curious  thick-walled  resting- spores 
or  zygospores.  The  zygospores  are  formed  on 
the  mycelium  buried  within  the  substance  on 
which  the  plant  grows.  They  originate  in  the 
following  way  :  Two  threads  that  lie  near  to- 
gether send  out  short  branches,  which  grow 
toward  each  other  and  finally  meet  (Fig.  273). 
The  walls  at  the  ends,  a,  then  disappear,  allow- 
ing the  contents  to  flow  together.  At  the  same 
time,  however,  two  other  walls  are  formed  at 
points  farther  back,  b,  b,  separating  the  short 
section,  c,  from  the  remainder  of  the  thread. 
This  section  now  increases  in  size  and  becomes 
covered  with  a  thick,  dark  brown  wall  orna- 
mented with  thickened  tubercles.  The  zygo- 
spore is  now  mature  and,  after  a  period  of 
rest,  it  germinates,  either  producing  a  sporan- 
gium directly  or  growing  out  as  mycelium. 
The  zygospores  of  the  mucors  form  one  of  the  most  interesting 
and  instructive  objects  among  the  lower  plants.  They  are,  how- 
ever, very  difficult  to  obtain.     One  of  the   mucors    {Sporoditiia 


Fig.  273.  —  Mucor, 
showing  formation 
of  zygospore  on 
the  right;  germi- 
nating zygospore 
on  the  left. 


190  PLANT  BIOLOGY 

grandis)  may  be  frequently  found  in  summer  growing  on  toad- 
stools. This  plant  usually  produces  zygospores  that  are  formed 
on  the  aerial  mycelium.  The  zygospores  are  large  enough  to  be 
recognized  with  a  hand  lens.  The  material  may  be  dried  and 
kept  for  winter  study,  or  the  zygospores  may  be  prepared  for 
permanent  microscopic  mounts  in  the  ordinary  way. 

Yeast.  —  This  is  a  very  much  reduced  and  simple  fungus,  con- 
sisting normally  of  isolated  spherical  or  elliptical  cells  (Fig.  275) 
containing  abundant  protoplasm   and  prob- 
ably a    nucleus,  although    the   latter  is    not 
easily   observed.      It   propagates   rapidly  by 
budding,  which  consists  of  the  gradual  extru- 
sion of  a  wart-like  swelling  that  is  sooner  or 
later  cut  off  at  the  base  by  constriction,  thus 
forming  a  separate  organism.     Although  sim- 
Fig  27=;  —Yeast       I^e  m   structure>   the  yeast  is  found   to   be 
'  Plants  closely  related  to  some  of  the  higher  groups  of 

fungi  as  shown  by  the  method  of  spore  forma- 
tion. When  grown  on  special  substances  like  potato  or  carrot,  the 
contents  of  the  cell  may  form  spores  inside  of  the  sac-like  mother 
cell,  thus  resembling  the  sac-fungi  to  which  blue  mold  and  mildews 
belong.  The  yeast  plant  is  remarkable  on  account  of  its  power  to 
induce  alcoholic  fermentation  in  the  media  in  which  it  grows. 

There  are  many  kinds  of  yeasts.  One  of  them  is  found  in  the 
common  yeast  cakes.  In  the  process  of  manufacture  of  these 
cakes,  the  yeast  cells  grow  to  a  certain  stage,  and  the  material  is 
then  dried  and  fashioned  into  small  cakes,  each  cake  containing 
great  numbers  of  the  yeast  cells.  When  the  yeast  cake  is  added 
to  dough,  and  proper  conditions  of  warmth  and  moisture  are  pro- 
vided, the  yeast  grows  rapidly  and  breaks  up  the  sugar  of  the 
dough  into  carbon  dioxid  and  alcohol.  This  is  fermentation. 
The  gases  escape  and  puff  up  the  dough,  causing  the  bread  to  rise. 
In  this  loosened  condition  the  dough  is  baked  ;  if  it  is  not  baked 
quickly  enough,  the  bread  "falls."  Shake  up  a  bit  of  yeast  cake 
in  slightly  sweetened  water  :  the  water  soon  becomes  cloudy  from 
the  growing  yeasts. 

Parasitic  fungi.  —  Most  of  the  molds  are  saprophytes.  Many 
other  fungi  are  parasitic  on  living  plants  and  animals  (Fig.  285). 
Some  of  them  have  complicated  life  histories,  undergoing  many 
changes  before  the  original  spore  is  again  produced.  The  willow 
mildew  and  the  common  rust  of 'wheat  will  serve  to  illustrate  the 
habits  of  parasitic  fungi. 

The  willow  mildew  {Uncinula  salicis).  —  This  is  one  of  the  sac 
fungi.     It  forms  white  downy  patches  on  the  leaves  of  willows 


STUDIES  IN   CRYPTOGAMS 


IQI 


Fig.  276. — Colonies  of  Willow  Mildew. 


(Fig.  276).  These  patches  consist  of  numerous  interwoven 
threads  that  may  be  recognized  under  the  microscope  as  the 
mycelium  of  the  fungus. 
The  mycelium  in  this 
case  lives  on  the  surface 
of  the  leaf  and  nour- 
ishes itself  by  sending 
short  branches  into  the 
cells  of  the  leaf  to  ab- 
sorb food  materials  from 
them. 

Numerous  summer-spores  are  formed  of  short,  erect  branches  all 
over  the  white  surface.     One  of  these  branches  is  shown  in  Fig. 

277.  When  it  has  grown  to  a  cer- 
tain length,  the  upper  part  begins 
to  segment  or  divide  into  spores 
which  fall  and  are  scattered  by  the 
wind.     Those  falling  on  other  wil- 

^S5  r^Pf' w  f \  V^  ^ows   reproduce   the  fungus  there. 

This  process  continues  all  summer, 
but  in  the  later  part  of  the  season 
provision  is  made  to  maintain  the 
mildew  through  the  winter.  If  some 
of  the  white  patches  are  closely  ex- 
amined in  July  or  August,  a  number 
of  little  black  bodies  will  be  seen  among  the  threads.  These  little 
bodies  are  called perithecia,  shown  in  Fig.  278.    To  the  naked  eye 

they  appear  as  minute  specks, 
but  when  seen  under  a  magnifi- 
cation of  200  diameters  they 
present  a  very  interesting  appear- 
ance. They  are  hollow  spheri- 
cal bodies  decorated  around 
the  outside 
with  a  fringe 
of  crook-like 
hairs.  The 
res  ting-spores 
of  the  willow 
mildew  are 
produced  in 
sacs  or  asci in- 
closed with- 
in the  leath- 

erv  perithecia.     Figure  279  shows  a  cross-section  of  a  perithecium 
with  the  asci  arising  from  the  bottom.    The  spores  remain  securely 


Fig. 


277.  —  Summer-spores  of 
Willow  Mildew. 


Fig.  278.  —  Perithecium  of  Wil- 
low Mildew. 


Fig.  279.  —  Section 
through  Peri- 
thecium of  Wil- 
low Mildew. 


\()2 


PLANT  BIOLOGY 


packed  in  the  perithecia.  They  do  not  ripen  in  the  autumn,  but 
fall  to  the  -round  with  the  leaf,  and  there  remain  securely  pro- 
tected among  the  dead  foliage.  The  following  spring  thev  mature 
and  are  liberated  by  the  decay  of  the  perithecia.  They  are  then 
ready  to  attack  the  unfolding  leaves  of  the  willow  and  repeat  the 
work  of  the  summer  before. 


FIG.  280.  —  Sori  CON- 
TAINING Teleuto- 
spores  of  Wheat 
Rust. 


The  wheat  rust.  —The  development  of  some  of  the  rusts,  as  the 
common  wheat  rust  {Puceinia  graminis),  is  even  more  interesting 

and  complicated  than  that  of  the 
mildews.  Wheat  rust  is  also  a  true 
parasite,  affecting  wheat  and  a  few 
other  grasses.  The  mycelium  here 
cannot  be  seen  by  the  unaided  eye, 
for  it  consists  of  threads  which  are 
present  within  the  host  plant,  mostly 
in  the  intercellular  spaces.  These 
threads  also  send  short  branches,  or 
haustoria  (Fig.  132),  into  the  neigh- 
boring cells  to  absorb  nutriment. 

The  res  ting-spores  of  wheat  rust 
are  produced  in  late  summer,  when 
they  may  be  found  in  black  lines 
breaking  through  the  epidermis  of 
the  wheat  stalk  (black-rust  stage). 
They  are  formed  in  masses,  called 
sort  (Fig.  280),  from  the  ends  of 
numerous  crowded  mycelial  strands  just  beneath  the  epidermis  of 
the  host.  The  individual  spores  are  very  small  and  can  be  well 
studied  only  with  a  microscope  of  high  power 
(X  about  400).  They  are  brown  two-celled  bod- 
ies with  a  thick  wall  (Fig.  281).  Since  they  are 
the  resting  or  winter-spores,  they  are  termed  tcleu- 
tospores  ("completed  spores").  Usually  they  do 
not  fall,  but  remain  in  the  sori  during  winter. 
The  following  spring  each  cell  of  the  teleutospore 
puts  forth  a  rather  stout  thread,  which  does  not 
grow  more  than  several  times  the  length  of  the 
spore  and  terminates  in  a  blunt  extremity.  This 
germ  tube,  promycelium,  now  becomes  divided 
into  four  cells  by  cross  walls,  which  are  formed 
from  the  top  downwards.  Each  cell  gives  rise  to  a  short,  pointed 
branch  which,  in  the  course  of  a  few  hours,  forms  at  its  summit 
a  single  spore  called  a  sporidium.  This  in  turn  germinates  and 
produces  a  mycelium.  In  Fig.  282  a  germinating  teleutospore 
is  drawn  to  show  the  promycelium,  p,  divided  into  four  cells, 


Fig.  281.  — Te- 
leutospore 
of  Wheat 
Rust. 


STUDIES  IN  CRYPTOGAMS 


193 


each  producing  a  short  branch  with  a  little  spo- 
ridium,  s. 

A  most  remarkable  circumstance  in  the  life 
history  of  the  wheat  rust  is  the  fact  that  the  my- 
celium produced  by  the  sporidium  can  live  only 
in  barberry  /eaves,  and  it  follows  that  if  no  bar- 
berry bushes  are  in  the  neighborhood  the  sporidia 
finally  perish.  Those  which  happen  to  lodge  on 
a  barberry  bush  germinate  immediately,  produc- 
ing a  mycelium  that  enters  the  barberry  leaf  and 
grows  within  its  tissues.  Very  soon  the  fungus 
produces  a  new  kind  of  spores  on  the  barberry 
leaves.  These  are  called  <zcidiospores.  They  are 
formed  in  long  chains  in  little  fringed  cups,  or 
cecidia,  which  appear  in  groups  on  the  lower  side 
of  the  leaf  (Fig.  283).  These  orange  or  yellow 
aecidia  are  termed  cluster-cups.  In  Fig.  284  is 
shown  a  cross-section  of  one  of  the  cups,  outlin- 
ing the  long  chains  of  spores,  and  the  mycelium  in  the  tissues. 

The  secidiospores  are  formed  in  the  spring,  and  after  they  have 
been  set  free,  some  of  them  lodge  on  wheat  or  other  grasses, 
where  they  germinate  immediately.      The  germ-tube  enters  the 


Fig.  282.  —  Ger- 
minating Te- 
leutospore 
of  Wheat 
Rust. 


Fig.  283.  —  Leaf 
of  Barberry 
with  Clus- 
ter-cups. 


Fig.  284. —Section  through  a 
Cluster-cup  on  Barberry  Leaf. 


leaf  through  a  stomate,  whence  it  spreads  among  the  cells  of  the 
wheat  plant.  In  summer  one-celled  reddish  uredospores  ("blight 
spores,"  red-rust  stage)  are  produced  in  a  manner  similar  to  the 
teleutospores.     These  are   capable  of  germinating  immediately, 


194 


PLANT  BIOLOGY 


and  serve  to  disseminate  the  fungus  during  the  summer  on  other 
wheat  plants  or  grasses.  Late  in  the  season,  teleutospores  are 
again  produced,  completing  the  life  cycle  of  the  plant. 

Many  rusts  besides  Puccinia  graminis  produce  different  spore 
forms  on  different  plants.  The  phenomenon  is  called  hetereecisni, 
and  was  first  shown  to  exist  in  the  wheat  rust.  Curiously  enough, 
the  peasants  of  Kurope  had  observed  and  asserted  that  barberry 
bushes  cause  wheat  to  blight  long  before  science  explained  the 
relation  between  the  cluster-cups  on  barberry  and  the  rust  on 
wheat.  The  true  relation  was  actually  demonstrated,  as  has  since 
been  done  for  many  other  rusts  on  their  respective  hosts,  by  sow- 
ing the  ascidiospores  on  healthy  wheat  plants  and  thus  producing 


Anthracnose  CanKer 


5tarc.lt  Grains 


Fig.  285.  —  How  a  Parasitic  Fungus  works.    Anthracnose  on  a  bean  pod 
entering  the  bean  beneath.     (Whetzel.) 

the  rust.  The  cedar  apple  is  another  rust,  producing  the  curious 
swellings  often  found  on  the  branches  of  red  cedar  trees.  In  the 
spring  the  teleutospores  ooze  out  from  the  "  apple  "  in  brown- 
ish yellow  masses.  It  has  been  found  that  these  attack  various 
fruit  trees,  producing  aecidia  on  their  leaves.  Fig.  285  explains 
how  a  parasitic  fungus  works. 


Puffballs,  mushrooms,  toadstools,  and  shelf  fungi •■ — These 
represent  what  are  called  the  higher  fungi,  because  of  the  size  and 
complexity  of  the  plant  body  as  well  as  from  the  fact  that  they 
seem  to  stand  at  the  end  of  one  line  of  evolution.  The  mycelial 
threads  grow  together  in  extensive  strands  in  rotten  wood  or  in 
the  soil,  and  send  out  large  complex  growths  of  mycelium  in  con- 


STUDIES  IN   CRYPTOGAMS 


195 


Fig.  286.  —  Part  of  Gill  of  the  Cul- 
tivated Mushroom. 

tr,  trama  tissue;  sh,  hymenium;  b,  basidium; 
si,  sterigma;  sp,  spore.     (Atkinson.) 


nection  with  which  the  spores  are  borne.  These  aerial  parts  are 
the  only  ones  we  ordinarily  see,  and  which  constitute  the  "  mush- 
room "  part  (Fig.  131  ). 
Only  asexual  spores  (ba- 
sidiospores)  are  produced, 
and  on  short  stalks  {basidia  t 
(Fig.  286).  In  the  puff- 
balls  the  spores  are  inclosed 
and  constitute  a  large  part 
of  the  "smoke."  In  the 
mushrooms  and  toadstools 
they  are  borne  on  gills,  and 
in  the  shelf  fungi  (Fig.  134) 
on  the  walls  of  minute  pores 
of  the  underside.  The  my- 
celium of  these  shelf  fungi 
frequently  lives  and  grows 
for  a  long  time  concealed  in 
the  substratum  before  the 
visible  fruit  bodies  are  sent 
out.  Practically  all  timber 
decay  is  caused  by  such 
growth,  and  the  damage  is 
largely  done  before  the  fruiting  bodies  appear.  For  other  ac- 
counts of  mushrooms,  see  Chap.  XIV. 

Lichens 

Lichens  are  so  common  everywhere 
that  the  attention  of  the  student  is  sure 
to  be  drawn  to  them.  They  grow  on 
rocks,  trunks  of  trees  (Fig.  287),  old 
fences,  and  on  the  earth.  They  are 
thin,  usually  gray  ragged  objects,  ap- 
parently lifeless.  Their  study  is  too 
difficult  for  beginners,  but  a  few  words 
of  explanation  may  be  useful. 

Lichens  were   formerly  supposed  to 
be   a  distinct    or    separate  division  of 
plants.     They  are  now  known  to  be  or- 
ganisms, each  species  of  which  is  a  con- 
stant association  of  a  fungus  and  an  alga. 
The  thallus  is  ordinarily  made  up  of  fun- 
gous mycelium  or  tissue  within  which 
Fig.  287.  — Lichen  on  an      the   imprisoned   alga   is   definitely  dis- 
Oak  trunk.   (A  species      tributed.     The  result  is  a  growth  unlike 
of  Phvstia.}  either  component.     This  association  of 


iq6 


PLANT  BIOLOGY 


alga  and  fungus  is  usually  spoken  of  as  symbiosis,  or  mutually 
helpful  growth,  the  alga  furnishing  some  things,  the  fungus  others, 
and  both  together  being  able  to  accomplish  work  that  neither 
could  do  independently.  By  others  this  union  is  considered  to 
be  a  mild  form  of  parasitism,  in  which  the  fungus  profits  at  the 
expense  of  the  alga.  As  favorable  to  this  view,  the  facts  are  cited 
that  each  component  is  able  to  grow  independently,  and  that  under 
such  conditions  the  algal  cells  seem  to  thrive  better  than  when 
imprisoned  by  the  fungus. 

Lichens  propagate  by  means  of  soredia,  which  are  tiny  parts 
separated  from  the  body  of  the  thallus,  and  consisting  of  one  or 
more  algal  cells  overgrown  with  fungus  threads.  These  are  readily 
observed  in  many  lichens.  They  also  produce  spores,  usually 
ascospores,  which  are  always  the  product  of  the  fungus  element, 
and  which  reproduce  the  lichen  by  germinating  in  the  presence  of 
algal  cells,  to  which  the  hyphae  immediately  cling. 

Lichens  are  found  in  the  most  inhospitable  places,  and,  by 
means  of  acids  which  they  secrete,  they  attack  and  slowly  disin- 
tegrate even  the  hardest  rocks.  By  making  thin  sections  of  the 
thallus  with  a  sharp  razor  and  examining  under  the  compound 
microscope,  it  is  easy  to  distinguish  the  two  components  in  many 
lichens. 

Liverworts 

The  liverworts  are  peculiar  flat  green  plants  usually  found 
on  wet  cliffs  and  in  other  moist,  shady  places.  They  frequently 
occur    in   greenhouses   where    the    soil    is    kept   constantly   wet. 


Fig.  288.  Fig.  289. 

Plants  of  Marchantia. 


One  of  the  commonest  liverworts  is  Marchantia  polymorpha, 
two  plants  of  which  are  shown  in  Figs.  288,  289.  The  plant 
consists  of  a  ribbondike  thallus  that  creeps  along  the  ground, 
becoming  repeatedly  forked  as  it  grows.     The  end  of  each  branch 


STUDIES   IN   CRYPTOGAMS 


197 


is  always  conspicuously  notched.  There  is  a  prominent  midrib 
extending  along  the  center  of  each  branch  of  the  thallus.  On  the 
under  side  of  the  thallus,  especially  along  the  midrib,  there  are 
numerous  rhizoids  which  serve  the  purpose  of  roots;  absorbing 
nourishment  from  the  earth  and 
holding  the  plant  in  its  place.  The 
upper  surface  of  the  thallus  is  di- 
vided into  minute  rhombic  areas 
that  can  be  seen  with  the  naked 
eye.  Each  of  these  areas  is  per- 
forated by  a  small  breathing  pore 
or  stomate  that  leads  into  a  cavity 
just  beneath  the  epidermis.  This 
space  is  surrounded  by  chlorophyll- 
bearing  cells,  some  of  which  stand 
in  rows  from  the  bottom  of  the 
cavity  (Fig.  290).  The  delicate 
assimilating  tissue  is  thus  brought  in  close  communication  with  the 
outer  air  through  the  pore  in  the  thick,  protecting  epidermis. 

At  various  points  on  the  midrib  are  little  cups  containing 
small  green  bodies.  These  bodies  are  buds  or  gemma  which  are 
outgrowths  from  the  cells  at  the  bottom  of  the  cup.  They  become 
loosened  and  are  then  dispersed  by  the  rain  to  other  places,  where 
they  take  root  and  grow  into  new  plants. 

The  most  striking  organs  on  the  thallus  of  marchantia  are  the 
peculiar  stalked  bodies  shown  in  Figs.  288,  289.  These  are 
termed  archegoniophores  and  antheridiophores  or  receptacles.  Their 
structure  and  function  are  very  interesting,  but  their  parts  are  so 
minute  that  they  can  be  studied  only  with  the  aid  of  a  microscope 
magnifying  from  100  to  400  times.  Enlarged  drawings  will  guide 
the  pupil. 


Fig.  290. —  Section  of  Thallus 
OF  Marchantia.     Stomate  at  a. 


Fig.  291.  —  Section  through  Antheriiuophore  of  Marchantia, 
showing  antheridia.     One  antheridium  more  magnified. 

The  antheridiophores  are  fleshy,  lobed  disks  borne  on  short  stalks 
(Fig.  291 ).  The  upper  surface  of  the  disk  shows  openings  scarcely 
visible  to  the  naked  eye.  However,  a  section  of  the  disk,  such  as 
is  drawn  in  Fig.  291,  shows  that  the  pores  lead  into  oblong  cavi- 


I9S 


PLANT  BIOLOGY 


Fig.  292.— 

ARCHEi  .<  >- 
Nil  M    OF 

Marchantia. 


ties  in  the  receptacle.  From  the  base  of  each  cavity  there  arises 
a  thick,  club-shaped  body,  the  antheridium.  Within  the  anther- 
idium are  formed  many  sperm -cells  which  are  capa- 
ble of  swimming  about  in  water  by  means  of  long 
lashes  or  cilia  attached  to  them.  When  the  anther- 
idium is  mature,  it  bursts  and  allows  the  ciliated 
sperm  cells  to  escape. 

The  archegoniophores  are  also  elevated  on  stalks 
(Fig.  289).  Instead  of  a  simple  disk,  the  recepta- 
cle consists  of  nine  or  more  finger-like  rays.  Along 
the  under  side  of  the  rays,  between  delicately 
fringed  curtains,  peculiar  flask-like  bodies,  or  arche- 
gonia, are  situated.  The  archegonia  are  not  visible 
to  the  naked  eye.  They  can  be  studied  only  with 
the  microscope  (x  about  400).  One  of  them 
much  magnified  is  represented  in  Fig.  292.  Its 
principal  parts  are  the  long  neck,  a,  and  the 
rounded  venter,  b,  inclosing  a  large  free  cell  —  the 
egg-cell. 

We  have  seen  that  the  antheridium  at  maturity  discharges  its 
sperm-cells.  These  swim  about  in  the  water  provided  by  the  dew 
and  rain.  Some  of  them  finally  find  their  way 
to  the  archegonia  and  egg-cells,  the  latter 
being  fertilized,  as  pollen  fertilizes  the  ovules 
of  higher  plants. 

After  fertilization  the  egg-cell  develops  into 
the  spore  capsule  or  sporogonium.  The  mature 
spore  capsules  may  be  seen  in  Fig.  293.  They 
consist  of  an  oval  spore-case  on  a  short  stalk, 
the  base  of  which  is  imbedded  in  the  tissue  of 
the  receptacle,  from  which  it  derives  the  neces- 
sary nourishment  for  the  development  of  the 
sporogonium.  At  maturity  the  sporogonium 
is  ruptured  at  the  apex,  setting  free  the  spheri- 
cal spores  together  with  numerous  filaments 
having  spirally  thickened  walls  (Fig.  294).  These  filaments  are 
called  elaters.  When  drying,  they  exhibit  rapid  movements  by 
means  of  which  the  spores  are  scattered.  The  spores  germinate 
and  again  produce  the  thallus  of  marchantia. 


Fig.  293.  —  Arche- 
goniofhore, 

WITH   Sl'ORO- 

gonia,  of  Mar- 
chantia. 


294.  —  Spores  and  Elaters  of  Marchantia. 


STUDIES  IN  CRYPTOGAMS 


199 


Mosses  (Bryophyta) 

If  we  have  followed  carefully  the  development  of  marchantia, 
the  study  of  one  of  the  mosses  will  be  comparatively  easy.  The 
mosses  are  more  familiar  plants  than  the  liver- 
worts. They  grow  on  trees,  stones,  and  on  the 
soil  both  in  wet  and  dry  places.  One  of  the 
common  larger  mosses,  known  as  Polytrichum 
commune,  may  serve  as  an 
example,  Fig.  295.  This  plant 
grows  on  rather  dry  knolls, 
mostly  in  the  borders  of  open 
woods,  where  it  forms  large 
beds.  In  dry  weather  these 
beds  have  a  reddish  brown 
appearance,  but  when  moist 
they  form  beautiful  green 
cushions.  This  color  is  due, 
in  the  first  instance,  to  the 
color  of  the  old  stems  and 
leaves,  and,  in  the  second  in- 
stance, to  the  peculiar  action 
of  the  green  living  leaves 
under  the  influence  of  chang- 
ing moisture-conditions.  The 
inner  or  upper  surface  of  the 
leaf  is  covered  with  thin,  lon- 
gitudinal ridges  of  delicate 
cells  which  contain  chloro- 
phyll. These  cells  are  shown 
in  cross-section  in  Fig.  296,  as  dots  or  granules.  All  the  other 
tissue  of  the  leaf  consists  of  thick-walled,  corky  cells  which  do 


Fig.  295.  —  Polytrichum  commune. 

f,  /,  fertile  plants,  one  on  the  left  in  fruit, 
m,  antheriiial  plant. 


Fig.  296. —Section  of  Leaf  of  Polytrichum  commune. 

not  allow  moisture  to  penetrate.     When  the  air  is  moist  the  green 
leaves  spread  out,  exposing  the  chlorophyll  cells  to  the  air,  but  in 


200  PLANT  BIOLOGY 

dry  weather  the  margins  of  the  leaves  roll  inward,  and  the  leaves 
fold  closely  against  the  stem,  thus  protecting  the  delicate  assimi- 
lating tissue. 

The  antheridia  and  archegonia  of  polytrichum  are  borne  in 
groups  at  the  ends  of  the  branches  on  different  plants  (many 
mosses  bear  both  organs  on  the  same  branch).  They  are  sur- 
rounded by  involucres  of  characteristic  leaves  termed  perichcetia 
or  periductal  leai'es.  Multicellular  hairs  known  as paraphyses  are 
scattered  among  the  archegonia  and  antheridia.  The  involucres 
with  the  organs  borne  within  them  are  called  receptacles,  or.  le^s 
appropriately,  "  moss  flowers."  As  in  marchantia,  the  organs  are 
very  minute  and  must  be  highly  magnified  to  be  studied. 

The  antheridia  are  borne  in  broad  cup-like  receptacles  on  the 
antheridial  plants  (Fig.  297).     They  are  much  like  the  antheridia 

of  marchantia,  but  they  stand  free 
among  the  paraphyses  and  are  not 
sunk  in  cavities.  At  maturity  they 
burst  and  allow  the  sperm  cells  or 
spermatozoids  to  escape.  In  poly- 
trichum, when  the  receptacles  have 

fulfilled  their  function,  the  stem  con- 
Fig.  297.  -  Section  through  a      tinues  to  grow  from  the  center  0f 

receptacle    of     polytri-      the  cup  (w,  Fig.  295 ) .     The  arche- 

chum       commune,      showing  •  „  1  „•        ,(  ., 

. ,.       s      gonia  are  borne  in  other  receptacles 

paraphyses  and  antheridia.  ,.„.  ,  m,  ,., 

on  different  plants.  1  hey  are  like 
the  archegonia  of  marchantia  except  that  they  stand  erect  on  the 
end  of  the  branch. 

The  sporogonium  which  develops  from  the  fertilized  egg  is 
shown  in  a,  l>,  Fig.  295.  It  consists  of  a  long,  brown  stalk  bearing 
the  spore-case  at  its  summit.  The  base  of  the  stalk  is  imbedded 
in  the  end  of  the  moss  stem  by  which  it  is  nourished.  The 
capsule  is  entirely  inclosed  by  a  hairy  cap,  the  calvptra,  b.  The 
calyptra  is  really  the  remnant  of  the  archegonium,  which,  for  a 
time,  increases  in  size  to  accommodate  and  protect  the  young 
growing  capsule.  It  is  finally  torn  loose  and  carried  up  on  the 
spore-case.  The  mouth  of  the  capsule  is  closed  by  a  circular  lid, 
the  operculum,  having  a   conical  projection   at  the  center. 

The  operculum  soon  drops,  or  it  may  be  removed,  displaying  a 
fringe  of  sixty-four  teeth  guarding  the  mouth  of  the  capsule.  This 
ring  of  teeth  is  known  as  the  peristome.  In  most  mosses  the 
teeth  exhibit  peculiar  hygroscopic  movements  ;  i.e.  when  moist 
they  bend  outwards,  and  upon  drying  curve  in  toward  the  mouth 
of  the  capsule.  This  motion,  it  will  be  seen,  serves  to  disperse 
the  spores  gradually  over  a  long  period  of  time. 

Not  the  entire  capsule  is  filled  with  spores.  There  are  no 
elaters,  but  the  center  of  the  capsule  is  occupied  by  a  columnar 


STUDIES  IN  CRYPTOGAMS 


201 


strand  of  tissue,  the  columella,  which  expands  at  the  mouth  into  a 
thin,  membranous  disk,  closing  the  entire  mouth  of  the  capsule 
except  the  narrow  annular  chink  guarded  by  the 
teeth.  In  this  moss  the  points  of  the  teeth  are 
attached  to  the  margin  of  the  membrane,  allow- 
ing the  spores  to  sift  out  through  the  spaces  be- 
tween them. 

When  the  spores  germinate  they  form  a  green, 
branched  thread,  the  pro  tone  ma.  This  gives  rise 
directly  to  moss  plants,  which  appear  as  little 
buds  on  the  thread.  When  the  moss  plants  have 
sent  their  little  rhizoids  into  the  earth,  the  pro- 
tonema  dies,  for  it  is  no  longer  necessary  for  the 
support  of  the  little  plants,  and  the  moss  plants 
grow  independently. 

Funaria  is  a  moss  very  common  on  damp, 
open  soil.  It  forms  green  patches  of  small  fine 
leaves  from  which  arise  long  brown  stalks  termi- 
nated by  curved  capsules  (Fig.  298).  The  struc- 
ture is  similar  to  that  of  polytrichum,  except  the 
absence  of  plates  on  the  under  side  of  the  leaves, 
the  continuous  growth  of  the  stem,  the  curved 
capsule,  double  peristome,  monoecious  rather  than  dioecious  re 
ceptacles,  and  nearly  glabrous  unsymmetrical  calyptra. 


Fig.  298.  —  Fu- 
naria hy- 
groscopica. 


Equisetums,  or  Horsetails  (Pteridophyta) 

There  are  about  twenty-five  species  of  equisetum,  constituting 
the  only  genus  of  the  unique  family  Equisetacece.  Among  these 
E.  arvense  (Fig.  299)  is  common  on  clayey  and  sandy  soils. 

In  this  species  the  work  of  nutrition  and  that  of  spore 
production  are  performed  by  separate  shoots  from  an  underground 
rhizome.  The  fertile  branches  appear  early  in  spring.  The  stem, 
which  is  3  to  6  inches  high,  consists  of  a  number  of  cylindrical, 
furrowed  internodes,  each  sheathed  at  the  base  by  a  circle  of  scale 
leaves.  The  shoots  are  of  a  pale  yellow  color.  They  contain  no 
chlorophyll,  and  are  nourished  by  the  food  stored  in  the  rhizome 
(Fig.  299). 

The  spores  are  formed  on  specially  developed  fertile  leaves  or 
sporophxlls  which  are  collected  into  a  spike  or  cone  at  the  end  of 
the  stalk  (a,  Fig.  299).  A  single  sporophyll  is  shown  at  b.  It 
consists  of  a  short  stalk  expanded  into  a  broad,  mushroom-like 
head.  Several  large  sporangia  are  borne  on  its  under  side.  The 
spores  formed  in  the  sporangia  are  very  interesting  and  beautiful 


202 


PLANT    BIOLOGY 


objects  when  examined  under  the  microscope  (X  about  200).. 
They  are  spherical,  green  bodies,  each  surrounded  by  two  spiral 
bands  attached  to  the  spore  at  their  intersection,  s.  These  bands 
exhibit  hygroscopic  movements  by  means  of  which  the  spores  be- 
come entangled,  and  are  held  together.  This  is  of  advantage  to  the 
plant,  as  we  shall  see.  All  the  spores  are  alike,  but  some  of  the//v>- 
thallia  grow  to  a  greater  size  than  the  others.  The  large  prothallia 
produce  only  archegonia  while  the  smaller  ones  produce  antheridia. 
Both  of  these  organs  are  much  like  those  of  the  ferns,  and  fertili- 


FlG.  299.  —  Equisetum  arvense. 
st,  sterile  shoot;  f,  fertile  shoot  showing  the  spike  at  a ;  6,  sporophyll,  with  sporangia; 


zation  is  accomplished  in  the  same  way.  Since  the  prothallia  are 
usually  dioecious,  the  special  advantage  of  the  spiral  bands,  holding 
the  spores  together  so  that  both  kinds  of  prothallia  may  be  in 
close  proximity,  will  be  easily  understood.  As  in  the  fern,  the 
fertilized  egg-cell  develops  into  an  equisetum  plant. 

The  sterile  shoots  (st,  Fig.  299)  appear  much  later  in  the  season. 
They  give  rise  to  repeated  whorls  of  angular  or  furrowed  branches. 
The  leaves  are  very  much  reduced  scales,  situated  at  the  inter- 
nodes.  The  stems  are  provided  with  chlorophyll  and  act  as 
assimilating  tissue,  nourishing  the  rhizome  and  the  fertile  shoots. 
Nutriment  is  also  stored  in  special  tubers  developed  on  the  rhi- 
zome. 


STUDIES  IN  CRYPTOGAMS 


>03 


Other  species  of  equisetum  have  only  one  kind  of  shoot  —  a  tall, 
hard,  leafless,  green  shoot  with  the  spike  at  its  summit.  Equise- 
tum stems  are  full  of  silex,  and  they  are  sometimes  used  for  scour- 
ing floors  and  utensils  ;  hence  the  common  name  "  scouring  rush." 

Isoetes  (Pteridophyta) 

Isoetes  or  quilhvort  is  usually  found  in  water  or  damp  soil  on 
the  edges  of  ponds  and  lakes.  The  general  habit  of  the  plant  is 
seen  in  Fig.  300,  a.  It  consists 
of  a  short,  perennial  stem  bear- 
ing numerous  erect,  quill-like 
leaves  with  broad  sheathing  bases. 
The  plants  are  commonly  mis- 
taken for  young  grasses. 

Isoetes  bears  two  kinds  of 
spores,  large  roughened  ones, 
the  macrospores,  and  small  ones 
or  microspores.  Both  kinds  are 
formed  in  sporangia  borne  in  an 
excavation  in  the  expanded  base 
of  the  leaf.  The  macrospores  are 
formed  on  the  outer  and  the 
microspores  on  the  inner  leaves. 
A  sporangium  in  the  base  of  a 
leaf  is  shown  at  b.  It  is  partially 
covered  by  a  thin  membrane, 
the  velum.  The  minute  triangu- 
lar appendage  at  the  upper  end 
of  the  sporangium  is  called  the 
ligule. 

The  spores  are  liberated  by 
the  decay  of  the  sporangia.  They 
form  rudimentary  prothallia  of  two 
kinds.  The  microspores  produce 
prothallia  with  antheridia,  while 
the  macrospores  produce  pro- 
thallia with  archegonia.  Ferti- 
lization takes  place  as  in  the  mosses  or  liverworts,  and  the  fertilized 
egg-cell,  by  continued  growth,  gives  rise  again  to  the  isoetes  plant. 

Club-Mosses  (Pteridophyta) 

The  club-mosses  are  low  trailing  plants  of  moss-like  looks  and 
habit,  although  more  closely  allied  to  ferns  than  to  true  mosses. 
Except  one  genus  in  Florida,  all  our  club  mosses  belong  to  the 


Fig.  300.  —  Isoetes,  showing  habit 
of  plant  at  a  ;  b,  base  of  leaf,  show- 
ing sporangium,  velum,  and  ligule. 


204 


PLANT  BIOLOGY 


genus  Lycopodium.  They  grow  mostly  in  woods,  having  i -nerved 
evergreen  leaves  arranged  in  four  or  more  ranks.  Some  of  them 
make  long  strands,  as  the  ground  pine,  and  are  much  used  for 
Christmas  decorations.  The  spores  are  all  of  one  kind  or  form, 
borne  in  i-celled  sporangia  that  open  on  the  margin  into  two 
valves.     The   sporangia   are    borne    in   some  species  (Fig.  301) 


Fig.  301.  —A  Lycopodium 
with  Sporangia  in 
the  axii.s  of  the  fo- 
LIAGE Leaves.  {Lyco- 
podium lucidulum.) 


Fig.  302.  —  A  Ci.ub-moss 

{Lycopodium  complanatum) . 


as  small  yellow  bodies  in  the  axils  of  the  ordinary  leaves  near  the 
tip  of  the  shoot;  in  other  species  (Fig.  302)  they  are  borne 
in  the  axils  of  small  scales  that  form  a  catkin-like  spike.  The 
spores  are  very  numerous,  and  they  contain  an  oil  that  makes  them 
inflammable.  About  100  species  of  lycopodium  are  known. 
The  plants  grown  by  florists  under  the  name  of  lycopodium  are 
of  the  genus  Selaginella,  more  closely  allied  to  isoetes,  bearing 
two  kinds  of  spores  (microspores  and  macrospores). 


ANIMAL  BIOLOGY 


CHAPTER  I 

THE   PRINCIPLES   OF   BIOLOGY 

Biology  (Greek,  bios,  life;  logos,  discourse)  means  the 
science  of  life.  It  treats  of  animals  and  plants.  That 
branch  of  biology  which  treats  of  animals  is  called  zoology 
(Gr.  soon,  animal;  logos,  discourse).  The  biological 
science  of  botany  (Gr.  botane,  plant  or  herb)  treats  of 
plants. 

Living  things  are  distinguished  from  the  not  living  by  a 
series  of  processes,  or  changes  (feeding,  growth,  develop- 
ment, multiplication,  etc.),  which  together  constitute  what 
is  called  life.  These  processes  are  called  functions.  Both 
plants  and  animals  have  certain  parts  called  organs  which 
have  each  a  definite  work,  or  function;  hence  animals  and 
plants  are  said  to  be  organized.  For  example,  men  and 
most  animals  have  a  certain  organ  (the  mouth)  for  taking 
in  nourishment;  another  (the  food  tube),  for  its  digestion. 

Because  of  its  organization,  each  animal  or  plant  is  said 
to  be  an  organism.  Living  things  constitute  the  organic 
kingdom.  Things  without  life  and  not  formed  by  life 
constitute  the  inorganic,  or  mineral,  kingdom.  Mark  I  for 
inorganic  and  O  for  organic  after  the  proper  words  in  this 
list:  granite,  sugar,  lumber,  gold,  shellac,  sand,  coal,  paper, 
glass,  starch,  copper,  gelatine,  cloth,  air,  potatoes,  alcohol, 
oil,  clay.  Which  of  these  things  are  used  for  food  by 
animals?     Conclusion? 


ANIMAL    BIOLOGY 


Energy  in  the  Organic  World.  — We  see  animals  exerting 
energy;  that  is,  we  see  them  moving  about  and  doing 
work.  Plants  are  never  seen  acting  that  way;  yet  they 
need  energy  in  order  to  form  their  tissues,  grow,  and  raise 
themselves  in  the  air. 

Source  of  Plant  Energy.  —  We  notice  that  green  plants 
thrive  only  in  the  light,  while  animal  growth  is  largely  in- 
dependent of  light.  In  fact,  in  the  salt  mines  of  Poland 
there  are  churches  and  villages  below  the  ground,  and 
children  are  born,  become  adults,  and  live  all  their  lives 
below  ground,  without  seeing  the  sun.  (That  these  people 
are  not  very  strong  is  doubtless  due  more  to  want  of  fresh 
air  and  other  causes  than  want  of  sunlight.) 

The  need  of  plants  for 
sunlight  shozus  that  they 
must  obtain  something 
from  the  sun.  This  has 
been  found  to  be  energy. 
This  enables  them  to  lift 
their  stems  in  growth,  and  form  the  various  structures 
called  tissues  which  make  up  their  stems  and  leaves.  (See 
Part  I,  Chap.  XIII.)  It  is  noticed 
that  they  take  in  food  and  water 
from  the  soil  through  their  roots. 
Experiments  also  show  that  green 
plants  take  in  through  pores 
(Fig.  i),  on  the  under  side  of  their 
leaves,  a  gas  composed  of  carbon 
and  oxygen,  and  called  earbon 
dioxid.  The  energy  in  the  sunlight 
enables  the  plant  to  separate  out  the 
earbon  of  the  carbon  dioxid  and 
build  mineral  and  water  and  carbon 


Fig.  i.  —  Surfaces  of  a  Leaf, 
magnified. 


5"Water 


Fig.  2. —  A  Leaf  storing 
Energy  in  Sunlight. 


THE   PRINCIPLES   OF  BIOLOGY  3 

into  organic  substances.  The  oxygen  of  the  carbon  dioxid 
is  set  free  and  returns  to  the  air  (Fig.  2).  Starch,  sugar, 
oil,  and  woody  fiber  are  examples  of  substances  thus 
formed.  Can  you  think  of  any  fuel  not  clue  to  plants  ? 
How  Animals  obtain  Energy.  —  You  have  noticed  that 
starch,  oil,  etc.,  will  burn,  or  oxidize,  that  is,  unite  with  the 
oxygen  of  the  air;  thus  the  sun's  energy,  stored  in  these 
substances,  is  changed  back  to  heat  and  motion.  The 
oxidation  of  oil  or  sugar  may  occur  in  a  furnace;  it  may 
also  occur  in  the  living  substance  of  the  active  animal. 


FlG.  3.  —  Colorless  plants,  as  MUSH-      A  GREEN  leaf,  even  after  it  is  cut,  gives 
ROOMS,  give  off  no  oxygen.  off  oxygen  (O)  if  kept  in  the  sun. 


ery  little 

not  move 

notice  that 

r  food,  and 

If  the  sun- 


Fortunately  for  the  animals  the  plartts 
of  the  substances  built  up  by  them,  sine 
about  nor  need  to  keep  themselves  warm 
animals  are  constantly  using  plant  substancj 
constantly  drawing  the  air  into  thj^ftbodie 
light  had  not  enabled  the  green  ^Hnt  to  store  up  these 
substances  and  set  free  the  oxygen  (Fig.  3),  animals 
would  have  no  food  to  eat  nor  air  to  breathe;  hence  we 
may  say  that  the  sunlight  is  indirectly  the  source  of  the 
life  and  energy  of  animals.  Mushrooms  and  other  plants 
without  green  matter  cannot  set  oxygen  free  (Fig.  3). 


4  ANIMAL   BIOLOGY 

Experiment  to  show  the  Cause  of  Burning,  or  Oxidation. 

—  Obtain  a  large  glass  bottle  (a  pickle  jar),  a  short  candle, 
and  some  matches.  Light  the  candle  and  put  it  on  a  table 
near  the  edge,  and  cover  it  with  the  glass  jar.  The  flame 
slowly  smothers  and  goes  out.  Why  is  this  ?  Is  the  air 
now  in  the  jar  different  from  that  which  was  in  it  before 
the  candle  was  lighted  ?  Some  change  must  have  taken 
place  or  the  candle  would  continue  to  burn.  To  try 
whether  the  candle  will  burn  again  under  the  jar  without 
changing  the  air,  slide  the  jar  to  the  edge  of  the  table  and 
let  the  candle  drop  out.  Light  the  candle  and  slip  it  up 
into  the  jar  again,  the  jar  being  held  with  its  mouth  a  little 
over  the  edge  of  the  table  to  receive  the  candle  (Fig.  5). 
The  flame  goes  out  at  once.  Evidently  the  air  in  the  jar 
is  not  the  same  as  the  air  outside.  Take  up  the  jar  and 
wave  it  to  and  fro  a  few  times,  so  as  to  remove  the  old  air 
and  admit  fresh  air.  The  candle  now  burns  in  it  with  as 
bright  a  flame  as  at  first.  So  we  conclude  that  the  candle 
will  not  continue  to  burn  unless  there  is  a  constant  supply 
of  fresh  air.  The  gas  formed  by  the  burning  is  carbon 
dioxid.  It  is  the  gas  from  which  plants  extract  carbon. 
(See  Plant  Biology,  Chap.  V.)  One  test  for  the  presence 
of  this  gas  is  that  it  forms  a  white,  chalky  cloud  in  lime 
water ;  another  is  that  it  smothers  a  fire. 

Experiment  to  show  that  Animals  give  off  Carbon  Dioxid. 

—  Place  a  cardboard  over  the  mouth  of  a  bottle  containing 
pure  air.  Take  a  long  straw,  the  hollow  stem  of  a  weed, 
a  glass  tube,  or  a  sheet  of  stiff  paper  rolled  into  a  tube, 
and  pass  the  tube  into  the  bottle  through  a  hole  in  the 
cardboard.  Without  drawing  in  a  deep  breath,  send  one 
long  breath  into  the  bottle  through  the  tube,  emptying  the 
lungs  by  the  breath  as  nearly  as  possible  (Fig.  4).  Next 
invert  the  bottle  on  the  table  as  in  the  former  experiment, 


THE   PRINCIPLES    OE  BIOLOGY 


afterward  withdrawing  the  cardboard.  Move  the  bottle 
to  the  edge  of  the  table  and  pass  the  lighted  candle  up 
into  it  (Fig.  5).  Does  the  flame  go  out  as  quickly  as 
in  the  former  experiment  ? 

If  you  breathe  through  a  tube  into  clear  lime  water, 
the  water  turns  milky.  The  effect  of  the  breath  on  the 
candle  and  on  the  lime  water  shows  that  carbon  dioxid  is 
continually  leaving  our  bodies  in  the  breath. 


Fig.  4.  —  Breathing  into  a  bottle. i  Fig.  5.  —  Testing  the  air  in  the  bottle.1 

Oxidation  and  Deoxidation.  —The  union  of  oxygen  with 
carbon  and  other  substances,  which  occurs  in  fires  and 
in  the  bodies  of  animals,  is  called  oxidation.  The  separa- 
tion of  the  oxygen  from  carbon  such  as  occurs  in  the 
leaves  of  plants  is  called  deoxidation.  The  first  process 
sets  energy  free,  the  other  process  stores  it  up.  Animals 
give  off  carbon  dioxid  from  their  lungs  or  gills,  and  plants 
give  off  oxygen  from  their  leaves.  But  plants  need  some 
energy  in  growing,  so  oxidation  also  occurs  in  plants,  but 
to  a  far  less  extent  than  in  animals.  At  night,  because 
of  the  absence  of  sunlight,  no  deoxidation  is  taking  place 

1  From  Coleman's  "  Physiology  for  Beginners,"  Macmillan  Co.,  N.Y. 


L 


6  ANIMAL   BIOLOGY 

in  the  plant,  but  oxidation  and  growth  continue;  so  at 
night  the  plant  actually  breathes  out  some  carbon  dioxid. 
The  deepest  part  of  the  lungs  contains  the  most  carbon 
dioxid.  Why  was  it  necessary  to  empty  the  lungs  as 
nearly  as  possible  in  the  experiment  with  the  candle  ?  Why 
would  first  drawing  a  deep  breath  interfere  with  the  experi- 
ment ?  Why  does  closing  the  draught  of  a  stove,  thus 
shutting  off  part  of  the  air,  lessen  the  burning  ?  Why  does 
a  "  firefly  "  shine  brighter  at  each  breath  ?  Why  is  the  pulse 
and  breathing  faster  in  a  fever?     Very  slow  in  a  trance  ? 

The  key  for  understanding  any  animal  is  to  find  how 
it  gets  food  and  oxygen,  and  how  it  uses  the  energy 
thus  obtained  to  grow,  move,  avoid  its  enemies,  and  get 
more  food.     Because  it  moves,  it  needs  senses  to  guide  it. 

The  key  for  understanding  a  plant  is  to  find  how  it  gets 
food  and  sunlight  for  its  growth.  It  makes  little  provision 
against  enemies  ;  its  food  is  in  reach,  so  it  needs  no  senses 
to  guide  it.  The  plant  is  built  on  the  plan  of  having  the 
nutritive  activities  near  the  surface  (eg.  absorption  by  roots  ; 
gas  exchange  in  leaves).  The  animal  is  built  on  the  plan 
of  having  its  nutritive  activities  on  the  inside  (eg.  digestion ; 
breathing). 

Cell  and  Protoplasm.  —  Both  plants  and  animals  are 
composed  of  small  parts  called  cells.  Cells  are  usually 
microscopic  in  size.  They  have  various  shapes,  as  spheri- 
cal, flat,  cylindrical,  fiber-like,  star-shaped.  The  living 
substance  of  cells  is  called  protoplasm.  It  is  a  stiff,  gluey 
fluid,  albuminous  in  its  nature.  Every  cell  has  a  denser 
j^spot  or  kernel  called  a  nucleus,  and  in  the  nucleus  is  a  still 
smaller  speck  called  a  nucleolus.  Most  cells  are  denser  and 
tougher  on  the  outside,  and  are  said  to  have  a  cell  wall, 
but  many  cells  are  naked,  or  without  a  wall.  Hence  the 
indispensable  part  of  a  cell  is  not  the  wall  but  the  nucleus, 


THE   PRINCIPLES   OF  BIOLOGY 


and  a  cell  may  be  defined  as  a  bit  of  protoplasm  containing 
a  nucleus.  This  definition  includes  naked  cells  as  well  as 
cells  with  walls. 

One-celled  Animals.  —  There  are  countless  millions  of 
animals  and  plants  the  existence  of  which  was  not  sus- 
pected until  the  invention  of  the  micro-  ^ 

scope  several  centuries  ago.  They  are 
one-celled,  and  hence  microscopic  in  size.' 
It  is  believed  that  the  large  animals  and 
plants  are  descended  from  one-celled  ani- 
mals and  plants.  In  fact,  each  individual 
plant  or  animal  begins  life  as  a  single 
cell,  called  an  egg  cell,  and  forms  its 
organs  by  the  subdivision  of  the  egg  cell  into  many  cells. 
An  egg  cell  is  shown  in  Fig.  6,  and  the  first  stages  in  the 
development  of  an  egg  cell  are  shown  in  Fig.  7. 

The  animals  to  be  studied  in  the  first  chapter  are  one- 
celled  animals.     To  understand  them  we  must  learn  how 


Fig.  6.  —  Egg  cell  of 
mammal  with  yolk. 


Pig.  7.  —  Egg  cell  subdivides  into  many  cells  forming  a  sphere  (morula)  containing 
a  liquid.    A  dimple  forms  and  deepens  to  form  the  next  stage  (gastrula). 

they  eat,  breathe,  feel,  and  move.  They  are  called  Pro- 
tozoans (Greek  pjvtos,  first;  zoou,  life).  All  other  animals 
are  composed  of  many  cells  and  are  called  Metazoans 
(Greek  meta,  beyond  or  after).  The  cells  composing  the 
mucous  membrane  in  man  are  shown  in  Fig.  8.  The  cellu- 
lar structure  of  the  leaf  of  a  many-celled  plant  is  illustrated 
in  Fig.  1.     (See  also  Chap.  I,  Human  Biology.) 


8 


ANIMAL    RFOI.OGY 


Method  of  Classifying  Animals.  —  The  various  animals 
display  differences  more  or  less  marked.  The  question 
arises,  are  not  some  of  them  more  closely  related  than 
others  ?  We  conclude  that  they  are,  since  the  differ- 
ence between  some  animals  is  very  slight,  while  the 
difference  between  others  is  quite  marked. 

To  show  the  different  steps  in  classi- 
fying an  animal,  we  will  take  an  ex- 
ample,—  the  cow.  Even  little  children 
learn  to  recognize  a  cow,  although  indi- 
vidual cows  differ  somewhat  in  form, 
size,  color,  etc.  The  varieties  of  cows, 
such  as  short-horn,  Jersey,  etc.,  all 
form  one  species  of  animals,  having  the 
scientific  name  taunts.  Let  us  include 
in  a  larger  group  the  animals  closest 
akin  to  a  cow.  We  see  a  cat,  a  bison, 
and  a  dog  ;  rejecting  the  cat  and  the 
dog,  we  see  that  the  bison  has  horns, 
hoofs,  and  other  similarities.  We  in- 
clude it  with  the  cow  in  a  genus  called 
brane  formed  of  one    Bos,   calling  the  cow  Bos  taurus,  and 

layer  of  cells.     A  few  .  ,  .  ,  . 

cells  secrete  mucus.       the  bison,  Bos  bison.     The  sacred  cow 

of    India  (Bos  indicus)  is  so   like  the 

cow  and  buffalo  as  also  to  belong  in  the  genus  Bos.     Why 

is  not  the  camel,  which,  like  Bos  bison,  has  a  hump,  placed 

in  the  genus  Bos?     (Fig.  389.) 

The  Old  World  buffaloes,  —  most  abundant  in  Africa 
and  India, —the  antelopes,  sheep,  goats,  and  several  other 
genera  are  placed  with  the  genus  Bos  in  a  family  called 
the  Jiollow  horns. 

This  family,  because  of  its  even  number  of  toes  and 
the  habit  of  chewing  the  cud,  resembles  the  camel  family, 


THE  PRINCIPLES   OF  BIOLOGY  9 

the  deer  family,  and  several  other  families.  These  are  all 
placed  together  in  the  next  higher  systematic  unit  called 
an  order,  in  this  case,  the  order  of  ruminants. 

The  ruminants,  because  they  are  covered  with  hair 
and  nourish  the  young  with  milk,  are  in  every  essential 
respect  related  to  the  one-toed  horses,  the  beasts  of 
prey,  the  apes,  etc.  Hence  they  are  all  placed  in  a 
more  inclusive  division  of  animals,  the  class  called 
mammals. 

All  mammals  have  the  skeleton,  or  support  of  the 
body,  on  the  inside,  the  axis  of  which  is  called  the  verte- 
bral column.  This  feature  also  belongs  to  the  classes 
of  reptiles,  amphibians,  and  fishes.  It  is  therefore 
consistent  to  unite  these  classes  by  a  general  idea  or 
conception  into  a  great  branch  of  animals  called  the 
vertebrates. 

Returning  from  the  general  to  the  particular  by  succes- 
sive steps,  state  the  branch,  class,  order,  family,  genus, 
and  species  to  which  the  cow  belongs. 

The  Eight  Branches  or  Sub-kingdoms. — The  simplest 
classification  divides  the  whole  animal  kingdom  into 
eight  branches,  named  and  characterized  as  follows,  be- 
ginning with  the  lowest :  I.  Protozoans.  One-celled. 
II.  Sponges.  Many  openings.  III.  Polyps.  Circular; 
cup-like ;  having  only  one  opening  which  is  both  mouth  and 
vent.  IV.  Echinoderms.  Circular ;  rough-skinned ;  two 
openings.  V.  Mollusks.  No  skeleton  ;  usually  with  ex- 
ternal shell.  VI.  Vermes.  Elongate  body,  no  jointed  legs. 
VII.  Arthropods.  External  jointed  skeleton;  jointed 
legs.  VIII.  Vertebrates.  Internal  jointed  skeleton  with 
axis  or  backbone. 


\s- 


CHAPTER    II 

PROTOZOA    (One-celled   Animals) 

The  Ameba 


Suggestions.  —  Amebas  live  on  the  slime  found  on  submerged 
stems  and  leaves  in  standing  water,  or  in  the  ooze  at  the  bottom. 
Water  plants  may  be  crowded  into  a  glass  dish  and  allowed  to 
decay,  and  after  about  two  weeks  the  ameba  may  be  found  in 
the  brown  slime  scraped  from  the  plants.  An  ameba  culture 
sometimes  lasts  only  three  days.  The  most  abundant  supply 
ever  used  by  the  writer  was  from  a  bottle  of  water  where  some 
oats  were  germinating.  Use  }  or  }  inch  objective,  and  cover 
with  a  thin  cover  glass.  Teachers  who  object  to  the  use  of 
the  compound  microscope  in  a  first  course  should  require  a 
most  careful  study  of  the  figures. 


FIG.  9. —Ameba  PROTEUS,  much  enlarged. 


PROTOZOA 


I  I 


Fig.  io 


:>,  contractile  vacuole;  ec,  ectoplasm;  en, 
endoplasm;  n,  nucleus;  /s,  pseudopod; 
ps' ,  pseudopod  forming;  ectoplasm  pro- 
trudes and  endoplasm  flows  into  it. 


Form  and  Structure.  —  The  ameba  (also  spelled  amoeba) 
looks  so  much  like  a  clear  drop  of  jelly  that  a  beginner 
cannot  be  certain  that  he 
has  found  one  until  it  moves. 
It  is  a  speck  of  protoplasm 
(Fig.  9),  with  a  clear  outer 
layer,  the  ectoplasm ;  and  a 
granular,  internal  part,  the 
endoplasm.  Is  there  a  dis- 
tinct line  between  them  ? 
(Fig.  10.) 

Note  the  central  portion 
and  the  slender  prolonga- 
tions or  pseudopods  (Greek, 
false  feet).  Does  the  endoplasm  extend  into  the  pseudo- 
pods  ?  (Fig.  10.)  Are  the  pseudopods  arranged  with  any 
regularity  ? 

Sometimes  it  is  possible  to  see  a  denser  appearing  por- 
tion, called  the  nucleus  ;  also  a  clear  space,  the  contractile 
vacuole  (Fig.  10). 

Movements.  —  Sometimes  while  the  pseudopods  are  be- 
ing extended  and  contracted,  the  central  portion  remains 

in  the  same  place  (this  is  mo- 
tion). Usually  only  one  pseudo- 
pod is  extended,  and  the  body 
flows  into  it;  this  is  locomotion 
(Fig.  11).  There  is  a  new  foot 
made  for  each  step. 
Feeding.  —  If  the  ameba  crawls  near  a  food  particle,  the 
pseudopod  is  pressed  against  it,  or  a  depression  occurs  (Fig. 
12),  and  the  particle  is  soon  embedded  in  the  endoplasm. 
Often  a  clear  space  called  a.  food  vacuole  is  noticed  around 
the  food  particle.     This  is  the  water  that  is  taken  in  with 


Fig.  11.  —  The  same  ameba  seen 
at  different  times. 


12 


AN 'I MAI.    BIOLOGY 


JV1 


the  particle  (Fig.  12).  The  water  and  the 
particle  are  soon  absorbed  and  assimilated 
by  the  endoplasm. 

Excretion.  —  If  a  particle  of  sand  or  other 
indigestible  matter  is  taken  in,  it  is  left  bcJiind 
as  the  ameba  moves  on.  There  is  a  clear 
space  called  the  contractile  vacuole,  which 
slowly  contracts  and  disappears,  then  reap- 
pears and  expands  (Figs.  9  and  10).  This 
possibly  aids  in  excreting  oxidized  or  useless 
material. 

Circulation  in  the  ameba  consists  of  the 
movement  of  its  protoplasmic  particles.  It 
lacks  special  organs  of  circulation. 

Feeling.  — Jarring  the  glass  slide  seems  to 
be  felt,  for  it  causes  the  activity  of  the  ameba 
to  vary.  It  does  not  take  in  for  food  every 
particle  that  it  touches.  This  may  be  the 
beginning  of  taste,  based  upon  mere  chemical 
affinity.     The  pseudopods  aid  in  feeling. 

Reproduction.  —  Sometimes  an  ameba  is  seen 
dividing  into  two  parts.  A  narrowing  takes 
place  in  the  middle ;  the  nucleus  also  divides, 

a  part  going  to  each  portion  (Fig.  13).    The  mother  ameba 

finally  divides  into  two  daughter  amebas.     Sex  is  wanting. 
Source  of  the  Ameba's  Energy.  —  We  thus  see  that  the 

ameba  moves  without  feet,  eats  without  a  mouth,  digests 

without  a  stomach,   feels 

without    nerves,     and,    it 

should     also     be     stated, 

breathes    without    lungs, 

for    oxygen     is    absorbed 

from  the  water  by  its  wJiole  fig.  13.  — ameba,  dividing. 


Fig.  12.  —  The 
Ameba  tak- 
ing food. 


PROTOZOA  13 

surface.  Its  movements  require  energy  ;  this,  as  in  all  ani- 
mals, is  furnished  by  the  uniting  of  oxygen  with  the  food. 
Carbon  dioxid  and  other  waste  products  are  formed  by  the 
union  ;  these  pass  off  at  the  surface  of  the  ameba  and  taint 
the  water  with  impurities. 

Questions. —  Why  will  the  ameba  die  in  a  very  small  quantity  of 
water,  even  though  the  water  contains  enough  food?  Why  will  it  die 
still  quicker  if  air  is  excluded  from  contact  with  the  drop  of  water? 

The  ameba  never  dies  of  old  age.     Can  it  be  said  to  be  immortal? 

According  to  the  definition  of  a  cell  {Chapter  I),  is  the  ameba  a 
unicellular  or  multicellular  animal? 

Cysts.  —  If  the  water  inhabited  by  a  protozoan  dries  up, 
it  encysts,  that  is,  it  forms  a  tough  skin  called  a  cyst. 
Upon  return  of  better  conditions  it  breaks  the  cyst  and 
comes  out.  Encysted  protozoans  may  be  blown  through 
the  air :  this  explains  their  appearance  in  vessels  of  water 
containing  suitable  food  but  previously  free  from  proto- 
zoans. 

The  Slipper  Animalcule  or  Paramecium 

Suggestions.  —  Stagnant  water  often  contains  the  paramecium  as 
well  as  the  ameba  ;  or  they  may  be  found  in  a  dish  of  water  con- 
taining hay  or  finely  cut  clover,  after  the  dish  has  been  allowed  to 
stand  in  the  sun  for  several  days.  A  white  film  forming  on  the 
surface  is  a  sign  of  their  presence.  They  may  even  'be  seen  with 
the  unaided  eye  as  tiny  white  particles  by  looking  through  the  side 
of  the  dish  or  jar.  Use  at  first  a|or]  in.  objective.  Restrict 
their  movements  by  placing  cotton  fibers  beneath  the  cover  glass ; 
then  examine  with  4-  or  \  objective.     Otherwise,  study  figures. 

Shape  and  Structure. — The  Paramecium's  whole  body, 
like  the  ameba's,  is  only  one  cell.  It  resembles  a  slipper 
in  shape,  but  the  pointed  end  is  the  hind  end,  the  front  end 
being  rounded  (Fig.  14):  The  paramecium  is  propelled 
by  the  rapid  beating  of  numerous  fine,  threadlike  append- 


H 


A. XI  MA  I.    /l/O/.OGY 


ages  on  its  surface,  called  cilia  (Latin,  eyelashes)  (Figs.). 
The  cilia,  like  the  pseudopods  of  the  ameba,  are  merely 
prolongations  of  the  cell  protoplasm, 
but  they  are  permanent.  The  sepa- 
ration between  the  outer  ectoplasm 
and  the  interior  granular  endoplasm 
is  more  marked  than  in  the  ameba 
(Fig.  14). 

Nucleus  and  Vacuoles.  —  There  is 
a  large  nucleus  called  the  macro- 
nucleus,  and  beside  it  a 
smaller  one  called  the 
micronucleus.  They  are 
hard  to  see.  About  one 
third  of  the  way  from 
each  end  is  a  clear,  pul- 
sating space  (bb.  Fig. 
15)  called  the  pulsat- 
ing vacuole.  These 
spaces  contract  until 
they  disappear,  and  then 
reappear,  gradually  ex- 
panding. Tubes  lead  from  the  vacuoles  which  probably 
serve  to  keep  the  contents  of  the  cell  in  circulation. 

Feeding. — A  depression,  or  groove,  is  seen  on  one  side, 
this  serves  as  a  mouth  (Figs.).     A  tube  which  serves  as  a 

gullet  leads  from  the 
mouth-groove  to  the  in- 
M<>.  terior  of  the  cell.  The 
mouth-groove  is  lined 
with    cilia    which    sweep 

food      particles      inward. 
Fig.  16.  —  Two  Paramecia  exchanging 

parts  of  their  nuclei.  The  particles  accumulate 


Fig.  14.  —  Paramecium, 

show  ing  cilia,  c. 

Two  contractile  vacuoles,  cv; 
the  macronucleus,  mg\ 
two  micronuclei,  mi;  the 
gullet  (<2T),  a  food  ball 
forming  and  ten  food  balls 
in  their  course  from  gullet 
to  vent,  a. 


PROTOZOA 


15 


in  a  mass  at  the  inner  end  of  the  gullet,  become  separated 
from  it  as  a  food  ball  (Fig.  14),  and  sink  into  the  soft  pro- 
toplasm of  the  body.  The  food  balls 
follow  a  circular  course  through  the 
endoplasm,  keeping  near  the  ectoplasm. 
Reproduction.  —  This,  as  in  the  ameba, 
is  by  division,  the  constriction  being  in 
the  middle,  and  part  of  the  nucleus  going 
to  each  half.  Sometimes  two  individ- 
uals come  together  with  their 
mouth-grooves  touching  and 
exchange  parts  of  their  nuclei 
(Fig.  16).  They  then  separate 
and  each  divides  to  form  two 
new  individuals. 

We  thus  see  that  the  Para- 
mecium, though  of  only  one 
cell,  is  a  much  more  complex  and  advanced 
animal  than  the  ameba.  The  tiny  paddles, 
or  cilia,  the  mouth-groove,  etc.,  have  their 
special  duties  similar  to  the  specialized  organs 
of  the  many-celled  animals  to  be  studied  later. 

If  time  and  circumstances 
allow  a  prolonged  study,  sev- 
eral additional  facts  may  be 
observed  by  the  pupil,  e.g. 
Does  the  paramecium  swim 
with  the  same  end  always 
foremost,  and  same  side 
uppermost  ?  Can  it  move 
backwards  ?  Avoid  obsta- 
cles ?  Change  shape  in  a 
narrow  passage  ?   Does  refuse    fig.  19.— Shell  of  a  Radiolarian 


Fig.  17.  —  Vorti- 
cella  (or  bell 
animalcule),  two 
extended,        one 

withdrawn. 


1 6  ANIMAL   BIOLOGY 

matter  leave  the  body  at  any  particular  place  ?  Trace 
movement  of  the  food  particles. 

Draw  the  paramecium. 

Which  has  more  permanent  parts,  the  ameba  or  Para- 
mecium :?  Name  two  anatomical  similarities  and  three  dif- 
ferences ;  four  functional  similarities  and  three  differences. 

The  ameba  belongs  in  the  class  of  protozoans  called 
Rhizopoda  "root  footed." 

Other  classes  of  Protozoans  are  the  Tnfusorians,  which 
have  many  waving  cilia  (Fig.  17)  or  one  whip-like  flagellum 
(Fig.  18),  and  the  Foraminifers  which  possess  a  calcareous 
shell  pierced  with  holes.  Much  chalky  limestone  has  been 
formed  of  their  shells.  These  and  the  radiolarians,  which 
have  flinty  shells  (Fig.  19),  are  often  placed  in  the  class 
rhizopoda.     To  which  class  does  the  paramecium  belong  ? 

Protozoans  furnish  a  large  amount  of  food  to  the  higher 

animals. 

To  the  Teacher.  If  plant,  animal,  and  human  biology  are  to  be 
given  in  one  year  as  planned,  and  full  time  allowed  for  practical  work, 
the  portions  of  the  text  in  small  type,  as  Chapter  III,  may  be  omitted 
or  merely  read  and  discussed.  Any  two  of  the  three  parts  forming  the 
course  may  be  used  for  a  years  course  by  using  all  of  the  text  and 
spending  more  time  on  practical  and  field  work. 


CHAPTER    III 


SPONGES 


Suggestions.  —  In  man}-  parts  of  the  United  States,  fresh-water 
sponges  may.  by  careful  searching,  be  found  growing  on  rocks  and  logs 
in  clear  water.  They  are  brown,  creamy,  or  greenish  in  color,  and  re- 
semble more  a  cushion-like  plant  than  an  animal.  They  have  a  char- 
acteristic gritty  feel.     They  soon  die  after  removal  to  an  aquarium. 

A  number  of  common  small  bath  sponges  may  be  bought  and  kept 
for  use  in  studying  the  skeleton  of  an  ocean  sponge.  These  sponges 
should  not  have  large 
holes  in  the  bottom ;  if 
so,  too  much  of  the 
sponge  has  been  cut 
away.  A  piece  of  marine 
sponge  preserved  in  alco- 
hol or  formalin  may  be 
used  for  showing  the 
sponge  with  its  flesh  in 
place.  Microscopic  slides 
may  be  used  for  showing 
the  spicules. 

The  small  fresh-water 

sponge    (Fig.  21)    lacks 
r  ,  Fig.  21.  — Fkesh-water  Sponge. 

the  more  or  less  vase- 
like  form   typical   of  sponges.       It    is   a  rounded   mass   growing 
upon  a  rock  or  log.     As  indicated  by  the  arrows,  where  does 

water  enter  the  sponge?  This 
may  be  tested  by  putting  color- 
ing matter  in  the  water  near 
the  living  sponge.  Where  does 
the  water  come  out}  (Fig.  22.) 
Does  it  pass  through  ciliated 
chambers  in  its  course?    Is  the 


a 

Fig.  22.  —  Section  of  fresh-water  sponge 
(enlarged). 

c  17 


iS 


AX  I  MA  I.    BIOLOGY 


Fie.  23. —  EGGS  and  SPICULES  of  fresh-water 
sponge  (enlarged). 


V^vjjfc. ' 


surface  of  the  sponge  rough  or  smooth?  Do  any  of  the  skeletal 
spicules  show  on  the  surface?  (Fig.  21.)  Does  the  sponge  thin 
out  near  its  edge? 

The  egg  of  this  sponge  is  shown  in  Fig.  23.     It  escapes  from 
the   parent  sponge  through  the  osculum,  or  large  outlet.     As  in 

most  sponges,  the  first 
stage  after  the  egg  is 
ciliated  and  free-swim- 
ming. 

Marine  Sponges.  — 
The  grantia  (Fig.  24)  is 
one  of  the  simplest  of 
marine  sponges.  What  is  the  shape  of  grantia?  What  is  its  length 
and  diameter?  How  does  the  free  end  differ  from  the  fixed  end? 
Are  the  spicules  projecting  from  its  body  few  or  many? 
Where  is  the  osculum,  or  large  outlet?  With  what 
is  this  surrounded?  The  osculum  opens  from  a  central 
cavity  called  the  cloaca.  The  canals  from  the  pores 
lead  to  the  cloaca. 

Buds  are  sometimes  seen  growing  out  from  the 
sponge  near  its  base.  These  are  young  sponges  formed 
asexually.  Later  they  become  detached  from  the 
parent  sponge. 

Commercial  "  Sponge."  —  What  part  of  the  complete 
animal  remains  in  the  bath  sponge?  Slow  growing 
sponges  grow  more  at  the  top  and  form  tall,  simple, 
tubular  or  vase-like  animals.  Fast  growing  sponges 
grow  on  all  sides  at  once  and  form  a  complicated  system  of  canals, 
pores,  and  oscula.  Which  of  these  habits  of  growth  do  you  think 
belonged  to  the  bath  sponge?  Is  there  a  large 
hole  in  the  base  of  your  specimen  ?  If  so,  this 
is  because  the  cloaca  was  reached  in  trimming 
the  lower  part  where  it  was  attached  to  a  rock. 
Test  the  elasticity  of  the  sponge  when  dry  and 
when  wet  by  squeezing  it.  Is  it  softer  when  wet 
or  dry?  Is  it  more  elastic  when  wet  or  dry? 
How  many  oscula  does  your  specimen  have? 
a  sponge.  How  many  inhalent  pores  to  a  square   inch  ? 


Fig.  24.— 

Grantia. 


SPONGES 


19 


Using  a  probe  (a  wire  with  knob  at  end,  or  small  hat  pin),  try 
to  trace  the  canals  from  the  pores  to  the  cavities  inside. 

Do  the  fibers  of  the  sponge  appear  to 
interlace,  or  join,  according  to  any  system? 
Do  you  see  any  fringedike  growths  on  the 
surface  which  show  that  new  tubes  are  be- 
ginning to  form?  Was  the  sponge  growing 
faster  at  the  top,  on  the  sides,  or  near  the 
bottom? 

Burn  a  bit  of  the  sponge  ;  from  the  odor, 
what  would  you  judge  of  its  composition? 
Is  the  inner  cavity  more  conspicuous  in  a  simple  sponge  or  in  a 
compound  sponge   like  the  bath   sponge?     Is   the   bath  sponge 


Fig.  26.  —  Batii  sponge. 


FlG.  27.  —  Bath  Sponge. 


bain  Sponge. 


branched  or  lobed?  Compare  a  number  of  specimens  (Figs.  26, 
27,  28)  and  decide  whether  the  common  sponge  has  a  typical 
shape.  What  features  do  their  forms 
possess  in  common? 

Sponges  are  divided  into  three  classes, 
according  as  their  skeletons  are  flinty 
(silicious),  limy  (calcareous),  or  horny. 

Some  of  the  silicious  sponges  have 
skeletons  that  resemble  spun  glass  in 
their  delicacy.  Flint  is  chemically  nearly 
the  same  as  glass.  The  skeleton  shown 
in  Fig.  29  is  that  of  a  glass  sponge  which 
lives  near  the  Philippine  Islands. 

The   horny  sponges  do  not   have   spi- 
cules in  their  skeletons,  as  the  flinty  and 
limy    sponges    have,    but    the    skeleton 
glass  sponge.  is   composed   of  interweaving    fibers   of 


20 


ANIMAL   BIOLOGY 


spongin,  a  durable  substance  of  the  same  chemical  nature  as  silk 
(Figs.  30  and  31). 

The  limy  sponges  have  skeletons  made  of  numerous  spicules  of 
lime.     The  three-rayed  spicule  is  the  commonest  form. 

The  commercial  sponge,  seen  as  it  grows  in  the  ocean,  appears 
as  a  roundish  mass  with  a  smooth,  dark  exterior,  and  having  about 
the  consistency  of  beef  liver.  Several  large  openings  (oscula), 
from  which  the  water  flows,  are  visible  on  the  upper  surface. 
Smaller  holes  (inhalent  pores  —  many  of  them  so  small  as  to  be 
indistinguishable)  are  on  the  sides.     If  the  sponge  is  disturbed, 

the  smaller  holes,  and 
perhaps  the  larger 
ones,  will  close. 

The  outer  layer  of 
cells  serves  as  a  sort 
of  skin.  Since  so 
much  of  the  sponge 
is  in  contact  with 
water,  most  of  the 
cells  do  their  own 
breathing,  or  absorp- 
tion of  oxygen  and  giving  off  of  carbon  dioxid.  Nutriment  is 
passed  on  from  the  surface  cells  to  nourish  the  rest  of  the  body. 

Reproduction.  —  Egg-cells  and  sperm-cells  are  produced  by 
certain  cells  along  the  canals.  The  egg-cell,  after  it  is  fertilized 
by  the  sperm-cell,  begins  to  divide  and  form  new  cells,  some  of 
which  possess  cilia.  The  embryo  sponge  passes  out  at  an  oscu- 
lum.  By  the  vibration  of  the  cilia,  it  swims  about  for  a  while. 
It  afterwards  settles  down  with  the  one  end  attached  to  the  ocean 
floor  and  remains  fixed  for  the  rest  of  its  life.  The  other  end  de- 
velops oscula.  Some  of  the  cilia  continue  to  vibrate  and  create 
currents  which  bring  food  and  oxygen. 

The  cilia  in  many  species  are  found  only  in  cavities  called 
ciliated  chambers.  (Figs.  22,  32.)  There  are  no  distinct  organs 
in  the  sponge  and  there  is  very  little  specialization  of  cells.  The 
ciliated  cells  and  the  reproductive  cells  are  the  only  specialized 
cells.  The  sponges  were  for  a  long  time  considered  as  colonies 
of  separate  one-celled  animals  classed  as  protozoans.     They  are, 


FIG.  31.— Section 
of  horny  sponge. 


SPOXGES 


21 


without  doubt,  many-celled  animals.      If  a  living  sponge  is  cut 
into  pieces,  each  piece  will  grow  and  form  a  complete  sponge. 

That  the  sponge  is  not  a  colony  of  one-celled  animals,  each  like 
an  ameba,  but  is  a  many-celled  animal,  will  be  realized  by  exam- 
ining Fig.  32,  which  shows  a  bit  of  sponge  highly  magnified.  A 
sponge  may  be  conceived  as  having  developed  from  a  one- celled 
animal  as  follows  :  Sev- 
eral one-celled  animals 
happened  to  live  side  by 
side ;  each  possessed  a 
thread-like  flagellum  (E, 
Fig.  32)  or  whip-lash  for 
striking  the  water.  By 
lashing  the  water,  they 
caused  a  stronger  cur- 
rent (Fig.  25)  than  pro- 
tozoans living  singly 
could  cause.  Thus  they 
obtained  more  food  and 
multiplied  more  rapidly 
than  those  living  alone. 
The  habit  of  working 
together  left  its  impress 
on  the  cells  and  was  trans- 
mitted by  inheritance. 

Cell  joined  to  cell 
formed  a  ring ;  ring 
joined  to  ring  formed  a  tube  which  was  still  more  effective  than 
a  ring  in  lashing  the  water  into  a  current  and  bringing  fresh  food 
(particles  of  dead  plants  and  animals)  and  oxygen. 

No  animals  eat  sponges  ;  possibly  because  spicules,  or  fibers, 
are  found  throughout  the  flesh,  or  because  the  taste  and  odor  is 
unpleasant  enough  to  protect  them.  Small  animals  sometimes 
crawl  into  them  to  hide.  One  species  grows  upon  shells  inhabited 
by  hermit  crabs.  Moving  of  the  shell  from  place  to  place  is  an 
advantage  to  them,  while  they  conceal  the  crab  and  thus  protect  it. 

Special  Report :  Sponge  "Fisheries."  (Localities;  how  sponges 
are  taken,  cleaned,  dried,  shipped,  and  sold.} 


FIG.  32. —  Microscopic  plan  of  ciliated  chamber. 
Each  cell  lining  the  chamber  has  a  nucleus, 
a  whip-lash,  and  a  collar  around  base  of 
whip-lash.  Question :  State  two  uses  of 
whip-lash. 


CHAPTER   IV 

POLYPS    (CUPLIKE   ANIMALS) 


Fig.  33.  — 
A  Hydra. 


The  Hydra,  or  Fresh  Water  Polyp 

Suggestions.  —  Except  in  the  drier  regions  of  the  United  States, 
the  hydra  can  usually  be  found  by  careful  search  in  fresh  water  ponds 
not  too  stagnant.  It  is  found  attached  to  stones,  sticks,  or  leaves, 
and  has  a  slender,  cylindrical  body  from  a  quarter  to  half  an 
inch  long,  varying  in  thickness  from  that  of  a  fine 
needle  to  that  of  a  common  pin.  The  green  hydra 
and  the  brown  hydra,  both  very  small,  are  common 
species,  though  hydras  are  often  white  or  colorless. 
They  should  be  kept  in  a  large  glass  dish  filled  with 
water.  They  may  be  distinguished  by  the  naked 
eye  but  are  not  studied  satisfactorily  without  a 
magnifying  glass  or  microscope.  Place  a  living  specimen  attached 
to  a  bit  of  wood  in  a  watch  crystal  filled  with  water,  or  on  a  hol- 
lowed slip,  or  on  a  slip  with  a  bit  of  weed  to  support  the  cover 
glass,  and  examine  with  hand  lens  or  lowest  power  of  microscope. 
Prepared  microscopical  sections,  both  transverse  and  longitudinal, 
may  be  bought 
of  dealers  in  mi- 
croscopic sup- 
plies. One  is 
shown  in  Fig.  39. 

Is  the  hy- 
dra's body- 
round  or  two- 
sided  ?  (Fig. 
35.)    What  is 

its  general  sliape  ?     Does  one   individual   keep  the   same 
shape?     (Fig.  34.)     How  does  the  length  of  the  thread- 


FlG.  34  —  Forms  assumed   by  Hydra. 


POLYPS   {CUPLIKE   ANIMALS) 


23 


like  tentacles  compare  with  the  length  of  the  hydra's  body  ? 
About  how  many  tentacles  are  on  a  hydra's  body  ?  Do  all 
have  the  same  number  of  tentacles  ?  Are  the  tentacles 
knotty  or  smooth  ?  (Fig.  35.)  The  hydra  is  usually  ex- 
tended and  slender  ;  sometimes  it  is  contracted  and  rounded. 
In  which  of  these  conditions  is  the  base  (the  foot)  larger 
around  than  the  rest  of  the  body  ?  (Fig.  34.)  Smaller  ? 
How  many  openings  into  the 
body  are  visible  ?  Is  there  a 
depression  or  an  eminence  at 
the  base  of  the  tentacles  ?  For 
what  is  the  opening  on  top  of 
the  body  probably  used  ?  Why 
are  the  tentacles  placed  at  the 
top  of  the  hydra's  body  ?  Does 
the  mouth  have  the  most  con- 
venient location  possible  ? 

The  conical  projection  bear- 
ing the  mouth  is  called  Jiypo- 
stome  (Fig.  34).  The  mouth 
opens  into  the  digestive  cavity. 
Is  this  the  same  as  the  general 
body  cavity,  or  does  the  stomach  have  a  wall  distinct  from 
the  body  cavity  ?  How  far  down  does  the  body  cavity 
extend  ?     Does  it  extend  up  into  the  tentacles  ?     (Fig.  39.) 

If  a  tentacle  is  touched,  what  happens?  Is  the  body  ever  bent? 
Which  is  more  sensitive,  the  columnar  body  or  the  tentacles?  In 
searching  for  hydras  would  you  be  more  likely  to  find  the  ten- 
tacles extended  or  drawn  in?  Is  the  hypostome  ever  extended 
or  drawn  in?   (Fig.  34.) 

Locomotion. — -The  round  surface,  or  disk,  by  which  the 
hydra  is  attached,  is  called  its  foot.  Can  you  move  on 
one  foot  without  hopping  ?     The  hydra  moves  by  alter- 


Fig.  35.  —  Hydra  (much 
enlarged). 


24 


ANIMAL   BIOLOGY 


Fig.  36.  — Nettling  Cell. 

II.  discharged,  and  I.  not  discharged. 


nately  elongating  and  rounding  the  foot.  Can  you  dis- 
cover other  ways  by  which  it  moves  ?  Does  the  hydra 
always  stand  upon  its  foot  ? 

Lasso  Cells. — Upon  the  tentacles  (Fig.  35)  are  numer- 
ous cells  provided  each  with  a  thread-like  process  (Fig.  36) 

which  lies  coiled  within  the 
cell,  but  which  may  be 
thrown  out  upon  a  water 
flea,  or  other  minute  animal 
that  comes  in  reach.  The 
touch  of  the  lasso  paralyzes 
the  prey  (Fig.  37).  These 
cells  are  variously  called 
lasso  cells,  nettling  cells,  or 
thread  cells.  The  thread  is 
hollow  and  is  pushed  out  by  the  pressure  of  liquid  within. 
When  the  pressure  is  withdrawn  the  thread  goes  back  as 
the  finger  of  a  glove  may  be  turned  back  into  the  glove  by 
turning  the  finger  outside  in. 
When  a  minute  animal,  or 
other  particle  of  food  comes  in 
contact  with  a  tentacle,  how 
does  the  tentacle  get  the  food 
to  the  mouth  ?  By  bending 
and  bringing  the  end  to  the 
mouth,  or  by  shortening  and 
changing  its  form,  or  in  both 


ways  ?     (Fig.  34,  C.)     Do  the 
neighboring  tentacles  seem  to 
bend  over  to  assist  a  tentacle  in 
securing  prey?     (Fig.  34,  C.) 
Digestion.  —  The  food  parti- 

Fig.  37.  —  Hydra  capturing  a 
cles  break  up  before  remaining  vvater  flea 


POLYPS  (CUPLIKE   ANIMALS) 


25 


long  in  the  stomach,  and  the  nutritive  part  is  absorbed 
by  the  lining  cells,  or  endoderm  (Fig.  39).  The  indiges- 
tible remnants  go  out  through  the  mouth.  The  hydra  is 
not  provided  with  a  special  vent.  Why  could  the  vent  not 
be  situated  at  the  end  opposite  the  mouth  ? 

Circulation  and  Respiration.  —  Does  water  have  free 
access  to  the  body  cavity  ?  Does  the  hydra  have  few  or 
nearly  all  of  its  cells  exposed  to  the  water  in  which  it 
lives  ?  From  its  structure,  decide  whether  it  can  breathe 
like  a  sponge  or  whether 
special  respiratory  cells  are 
necessary  to  supply  it  with 
oxygen  and  give  off  carbon 
dioxid.  Blood  vessels  are 
unnecessary  for  transfer- 
ring oxygen  and  food  from 
cell  to  cell. 

Reproduction.  —  Do  you 
see  any  swellings  upon  the 
side  of  the  hydra  ?  (Fig.  34,  A.)  If  the  swelling  is  near 
the  tentacles,  it  is  a  spermary ;  if  near  the  base  it  is  an 
ovary.  A  sperm  coalesces  with  or  fertilizes  the  ovum  after 
the  ovum  is  exposed  by  the  breaking  of  the  ovary  wall. 
Sometimes  the  sperm  from  one  hydra  unites  with  the  ovum 
of  another  hydra.  This  is  called  cross-fertilization.  The 
same  term  is  applied  to  the  process  in  plants  when  the 
male  element,  or  pollen,  of  the  flower  unites  with  the 
ovules,  or  female  element,  of  the  flower  on  another  plant. 
The  hydra,  like  most  plants  and  some  other  animals,  is 
hermaphrodite,  that  is  to  say,  both  sperms  and  ova  are 
produced  by  one  individual.  In  the  autumn,  eggs  are 
produced  with  hard  shells  to  withstand  the  cold  until 
spring.     Sexual   reproduction   takes   place  when    food  is 


Fig.  38.  —  Hydras  on  pond  weed. 


26 


ANIMAL   BIOLOGY 


scarce.     Asexual  generation  (by  budding)  is  common  with 
the  hydra  when  food  supply  is  abundant.     After  the  bud 

grows  to  a  cer- 
tain size,  the 
outer  layer  of 
cells  at  the  base 
of  the  bud  con- 
stricts and  the 
young  hydra  is 
detached. 

Compare  the 
sponge  and  the 
hydra  in  the  fol- 
lowing respects: 
—  many  celled, 
or  one  celled ; 
obtaining  food  ; 
breathing;  tubes 
and  cavities ; 
openings ;  re- 
production ;  loco- 
motion. Which 
ranks        higher 


Fig. 


39- 


Longitudinal  section  of  hydra  (microscopic 
and  diagrammatic). 


among  the  metazoa  ?     The  metazoa,  or  many  celled  ani- 
mals, include  all  animals  except  which  branch  ? 

Figure  39  is  a  microscopic  view  of  a  vertical  section  of  a  hydra  to 
show  the  structure  of  the  body  wall.  There  is  an  outer  layer  called  the 
ectoderm,  and  an  inner  layer  called  the  endoderm.  There  is  also  a  thin 
supporting  layer  (black  in  the  figure)  called  the  mesoglea.  The  mesoglea 
is  the  thinnest  layer.  Are  the  cells  larger  in  the  endoderm  or  the  ectoderm  ? 
Do  both  layers  of  cells  assist  in  forming  the  reproductive  bud  ?  The  ecto- 
derm cells  end  on  the  inside  in  contractile  tails  which  form  a  thin  line  and 
have  the  effect  of  muscle  fibers.  They  serve  the  hydra  for  its  remarkable 
changes  of  shape.  When  the  hydra  is  cut  in  pieces,  each  piece  makes  a 
complete  hydra,  provided  it  contains  both  endoderm  and  ectoderm. 


POLYPS   {CUP LIKE  ANIMALS)  2 J 

In  what  ways  does  the  hydra  show  "  division  of  labor  ,1  ?  Answer 
this  by  explaining  the  classes  of  cells  specialized  to  serve  a  different 
purpose.  Which  cells  of  the  hydra  are  least  specialized?  In  what  par- 
ticulars is  the  plan  of  the  hydra  different  from  that  of  a  simple  sponge? 
An  ingenious  naturalist  living  more  than  a  century  ago,  asserted  that  it 
made  no  difference  to  the  hydra  whether  the  ectoderm  or  the  endoderm 
layer  were  outside  or  inside,  —  that  it  could  digest  equally  well  with 
either  layer.  He  allowed  a  hydra  to  swallow  a  worm  attached  to  a 
thread,  and  then  by  gently  pulling  in  the  thread,  turned  the  hydra  inside 
out.  More  recently  a  Japanese  naturalist  showed  that  the  hydra  could 
easily  be  turned  inside  out,  but  he  also  found  that  when  left  to  itself 
it  soon  reversed  matters  and  returned  to  its  natural  condition,  that 
the  cells  are  really  specialized  and  each  layer  can  do  its  own  work  and 
no  other. 

Habits.  —  The  hydra's  whole  body  is  a  hollow  bag,  the 
cavity  extending  even  into  the  tentacles.  The  tentacles 
may  increase  in  number  as  the  hydra  grows  but  seldom 
exceed  eight.  The  hydra  has  more  active  motion  than 
locomotion.  It  seldom  moves  from  its  place,  but  its  ten- 
tacles are  constantly  bending,  straightening,  contracting, 
and  expanding.  The  body  is  also  usually  in  motion,  bend- 
ing from  one  side  to  another.  When  the  tentacles  ap- 
proach the  mouth  with  captured  prey,  the  mouth  (invisible 
without  a  hand  lens)  opens  widely,  showing  five  lobes  or 
lips,  and  the  booty  is  soon  tucked  within.  A  hydra  can 
swallow  an  animal  larger  in  diameter  than  itself. 

The  endoderm  cells  have  ameboid  motion,  that  is,  they 
extend  pseudopods.  They  also  resemble  amebas  in  the 
power  of  intra-cellular  digestion  ;  that  is,  they  absorb  the 
harder  particles  of  food  and  digest  them  afterwards,  re- 
jecting the  indigestible  portions.  Some  of  these  cells  have 
flagella  (see  Fig.  39)  which  keep  the  fluid  of  the  cavity 
in  constant  motion. 

Sometimes  the  hydra  moves  after  the  manner  of  a  small 
caterpillar  called  a  "  measuring  worm,"  that  is,  it  takes 
hold  first  by  the  foot,  then  by  the  tentacles,   looping  its 


28 


ANIMAL    HJOLOGY 


00     V 

Fig.  40.—  Hydroid  Colony,  with 
nutritive  (P)  reproductive  (^l/)and 
defensive  (S)  hydranths. 


body  at  each  step.  Sometimes 
the  body  goes  end  over  end  in 
slow  somersaults. 

The  length  of  the  extended 
hydra  may  reach  one  half 
inch.  When  touched,  both 
tentacles  and  body  contract 
until  it  looks  to  the  unaided 
eye  like  a  round  speck  of 
jelly.  This  shows  sensibility, 
and  a  few  small  star-shaped 
cells  are  believed  to  be  nerve 

cells,   but  the   hydra  has  not  a  nervous  system.      Hydras 

show   their    liking   for    light   by  moving   to   the   side   of 

the  vessel  or  aquarium  whence  the  light  comes. 
The     Branch     Polyps 

(sometimes  called  Coelen- 

tcrata).  —  The   hydra  is 

the  only  fresh  water  rep- 
resentative of  this  great 

branch    of    the    animal 

kingdom.      This  branch 

is    characterized    by   its 

members     having     only 

one  opening  to  the  body. 

The  polyps  also  include 

the    salt   water    animals 

called     hydroids,     jelly- 
fishes,  and  coral  polyps. 
Hydroids.  —  Figure  40 

shows     a     hydro  id,      or 

group       of       hydra-like 

growths,   one    of    which 


Fig.  41.  — "  Portuguese  Man-o'-war  " 
(compare  with  Fig.  40).  A  floating 
hydroid  colony  with  long,  stinging  (and 
sensory)  streamers.  Troublesome  to 
bathers  in  Gulf  of  Mexico.  Notice 
balloon-like  float. 


POLYPS   {CUPLIKE  ANIMALS) 


29 


eats  and  digests  for  the  group,  another  defends  by  nettling 
cells,  another  produces  eggs.     Each  hydra-like  part  of  a 
hydroid  is  called  a  hydranth.     Sometimes  the  buds  on  the 
hydra  remain  attached  so  long  that  a  bud  forms  upon  the 
first  bud.     Thus  three  generations  are  represented  in  one 
organism.     Such  growths  show  us  that  it  is  not  always 
easy      to      tell 
what        consti- 
tutes   an    indi- 
vidual animal. 
Hydro  i  d  s 
may     be     con- 
ceived  to  Jiave 
been    developed 
by   the    failure 
of  budding  hy- 
dras    to    sepa- 
rate   from    the 
parent,  and  by 
the  gradual  formation  of  the  habit  of  living  together  and 
assisting  each  other.     When  each  hydranth  of  the  hydroid 
devoted  itself  to  a  special  function  of  digestion,  defense,  or 
reproduction,  this  group  lived  longer  and  prospered ;  more 
eggs  were  formed,  and  the  habits  of  the  group  were  trans- 
mitted to  a  more  numerous  progeny  than  were  the  habits 
of  a  group  where  members  worked  more  independently  of 
each  other. 

As  the  sponge  is  the  first,  lowest,  and  simplest  ex- 
ample of  the  devotion  of  special  cells  to  special  pur- 
poses, the  hydroid  is  the  first,  lowest,  and  simplest 
example  of  the  occurrence  of  organs,  that  is  of  special 
parts  of  the  body  (groups  of  cells)  set  aside  for  a 
special  work. 


Fig.  42. —The  formation  of  many  free  swimming  jelly- 
fishes  from  one  fixed  hydra-like  form.  The  saucer-like 
parts  (k)  turn  over  after  they  separate  and  become  like 
Fig.  43  or  44.     Letters  show  sequence  of  diagrams. 


30 


ANIMAL   BIOLOGY 


How  many  mature  hydranths  arc  seen   in  the  hydroid 
shown   in    Fig.   40  ?      Why   are   the   defensive    hydranths 

on  the  outside  of  the 
colony  ?  Which  hy- 
dranths have  no  tenta- 
cles ?     Why  not  ? 

Jellyfish.  —  Alterna- 
tion of  Generations.  — 
Medusa.  —  With  some 
species  of  hydroids,  a 
very  curious  thing  hap- 
pens. —  The  hydranth 
tJiat  is  to  produce  the 
eggs  falls  off  and  be- 
comes independent  of 
the  colony.  More  sur- 
prising still,  its  appear- 
ance changes  entirely  and  instead  of  being  hydra-like,  it 
becomes  the  large  and  complex  creature  called  jellyfish 
(Fig.  43)-  But 
the  egg  of  the 
jellyfish  pro- 
duces a  small 
hydra-like  ani- 
mal  which  gives 
rise  by  budding 
to  a  hydroid, 
and  the  cycle  is 
complete. 

The  bud  (or 
reproductive 
hydranth)  of 
the         hydroid 


fti 


Fig.  43.  — A  Jellyfish. 


pfclllll^lf 


Fig.  44. —  A  Jellyfish  (medusa). 


POLYPS  {CUPLIKE  ANIMALS) 


31 


does  not  produce  a  hydroid,  but  a  jellyfish ;  the  egg  of  the 
jellyfish  does  not  produce  a  jellyfish,  but  a  hydroid.  This  is 
called  by  zoologists,  alternation  of  generations.  A  complete 
individual  is  the  life  from  the  germination  of  one  egg  to 
the  production  of  another.  So  that  an  "individual"  con- 
sists of  a  hydroid  colony  fixed  in  one  place  together  with 
all  the  jellyfish  produced  from  its  buds,  and  which  may 
now  be  floating  miles  away  from  it  in  the  ocean.  Bathers 
in  the  surf  are  sometimes  touched  and  stung  by  the  long, 
streamer-like  tentacles  of  the  jellyfish.  These,  like  the 
tentacles  of  the  hydra,  have 
nettling  cells  (Fig.  41). 

The  umbrella-shaped  free 
swimming  jellyfish  is  called  a 
medusa  (Fig.  44). 

Coral  Polyps.  —  Some  of  the 
salt  water  relatives  of  the  hydra 
produce  buds  which  remain 
attached  to  the  parent  without, 
however,  becoming  different 
from  the  parent  in  any  way. 
The  coral  polyps  and  corallines  are  examples  of  colonies  of 
this  kind,  possessing  a  common  stalk  which  is  formed  as 
the  process  of  multiplication  goes  on.  In  the  case  of  coral 
polyps,  the  separate  animals  and  the  flesh  connecting  them 
secrete  within  themselves  a  hard,  limy,  supporting  structure 
known  as  coral.  In  some  species,  the  coral,  or  stony  part, 
is  so  developed  that  the  polyp  seems  to  be  inserted  in  the 
coral,  into  which  it  withdraws  itself  for  partial  protection 

(Fig.  45). 

The  corallines  secrete  a  smooth  stalk  which  affords 
no  protection,  but  they  also  secrete  a  coating  or  sheath 
which    incloses    both    themselves    and    the    stalk.     The 


Fig.  45.  — Coral  Polyps  (tenta- 
cles, a  multiple  of  six).  Notice 
hypostome. 


32 


ANIMAL   BIOLOGY 


coating    has    apertures    through    which    the    polyps   pro- 
trude in  order  to  feed  when  no  danger  is  near  (Fig.  46). 


Fig.  46.  —  Red  Coral- 
line with  crust  and 
polyps  [eight  tentacles) . 


Fig.  47.  —  Sea  Fan  (a  coralline). 


The  red  "  corals  "  used  for  jewelry  are  bits  of  stalks  of  cor- 
allines.    The  corallines  (Figs.  47,  48)  are  not  so  abundant 

,-v  nor    so     important 

W 

\      ■   ■    V     :'  ,'  "    ■      I       ■      '  '         '■•    *£" 


as  the  coral  polyps 
(Figs.  45,  49). 

Colonies  of  coral 
polyps  grow  in 
countless  numbers 
in  the  tropical  seas. 
The  coral  formed 
by  successive  colo- 
nies of  polyps  accu- 
mulates and  builds 
up  many  islands 
and  important  addi- 
tions to  continents.  The  Florida  "  keys,"  or  islands,  and 
the  southern  part  of  the  mainland  of  Florida  were  so 
formed. 


Fig.  48.  —  Organ  Pipe  "Coral"  (a  coralline). 


POLYPS  {CUPLIKE  ANIMALS) 


33 


The  Sea  Anemone,  like  the  coral 

polyp,   lives  in  the  sea,  but  like 

the  fresh  water  hydra,  it  deposits 

no  limy  support  for  its  body.     The 

anemone  is  much  larger  than  the 
hydra  and 
most  coral 
polyps, 
many  spe- 
cie s  at- 
taining a 
height  of 
several 
inches.  It 
does  not 
form  colo- 
nies.    When  its  arms  are  drawn  in, 

it  looks  like  a  large  knob  of  shiny  but  opaque  jelly.    Polyps 

used   to  be    called  zoophytes    {plant-animals),    because   of 

their  flower-like  appearance  (Figs.  50,  51). 

H 


Fig.  49. —  Upright  cut 
through  coral  polyp  X  4. 

ms,  mouth;  mr,  gullet;  Is, 
Is,  fleshy  partitions  (mesen- 
teries) extending  from  outer 
body  wall  to  gullet  (to  in- 
crease absorbing  surface) ; 
s,  s,  shorter  partitions;  mi, 
fb,  stony  support  (of  lime, 
called  coral) ;  t,  tentacles. 


OF  THE 


CHAPTER   V 


$= 


ECHINODERMS    (SPINY  ANIMALS) 

The  Starfish 


FIG.  52.  —  Starfish  on  a  rocky  shore. 


Suggestions.     Since  the  echinoderms  are  aberrant  though  inter- 
esting forms  not  in   the  regular  line  of  development  of  animals,  this 

chapter  may  be 
.».«£SG!fct  omitted     if     it 

is  desired  to 
shorten  the 

course.  —  The 
common  star- 
fish occurs 
along  the  At- 
lantic coast.  It 
is  captured  by 
wading  along 
the  shore  when 
the  tide  is  out. 

It  is  killed  by  immersion  in  warm,  fresh  water.  Specimens  are  usually 
preserved  in  4  per  cent  formalin.  Dried  starfish  and  sea  urchins  are  also 
useful.  A  living  starfish  kept 
in  a  pail  of  salt  water  will  be 
instructive. 

External      Features.  — 

Starfish  are  usually  brown 
or  yellow.  Why?  (See 
Fig.  52.)  Has  it  a  head  or 
tail?  Right  and  left  sides? 
What  is  the  shape  of  the 
disk,  or  part  which  bears 
the  five  arms  or  rays?  (Fig.  53.)  Does  the  body  as  a  whole 
have  symmetry  on  two  sides  of  a  line  (bilateral  symmetry),  or 
around  a  point  (radial  symmetry)  ?     Do  the  separate  rays  have 

34 


PLAN  of  starfish  ;   III,  madreporite. 


ECHTNODERMS   (SPEW  ANIMALS} 


35 


^mf-\ 


Fig.  54.  —  Limy  Plates 
in  portion  of  a  ray. 


FlG.  55.  —  Starfish  (sho\vin| 
Madreporite). 


bilateral  symmetry  ?   The  skeleton  consists  of  limy  plates  embedded 

in  the  tough  skin  (Fig.  54).     Is  the  skin  rough  or  smooth?    Hard 

or  soft?     Are  the  projections  (or  spines) 

in  the  skin  long  or  short?  The  skin  is 
hardened  by  the 
limy  plates,  ex- 
cept around  the 
mouth,  which  is 
at  the  center  of 

the  lower  side  and  surrounded  by  a  mem- 
brane. Which  is  rougher,  the  mouth  side, 
(oralsx&e.)  or  the  opposite  (aboral  side)? 
Which  side  is  more  nearly  flat  ?  The 
vent  is  at  or  near  the  center  of  the 
disk  on  the  aboral  surface.     It  is  usually 

very  small  and  sometimes  absent.     Why  a  vent  is  not  of  much 

use  will  be  understood  after  learning  how  the  starfish  takes  food. 
An  organ  peculiar  to  animals  of  this 

branch,  and  called  the  madreporic  plate, 

or  madreporite,  is  found  on  the  aboral 

surface  between  the  bases  of  two  rays 

(Fig.  55).     It  is  wartlike,   and  usually 

white  or  red.     This  plate  is  a  sieve  ;  the 

small  openings  keep  out  sand  but  allow 

water  to  filter  through. 

Movements  :   the  Water-tube  System. 

—  The  water,  which  is  filtered  through 

the  perforated   madreporite,  is  needed 

to  supply  a  system  of  canals  (Fig.  56). 

The   madreporite    opens    into    a    canal 

called  the  stone  canal,  the  wall  of  which 

is  hardened  by  the  same  kind  of  mate- 
rial as  that  found  in  the  skin.     The  stone 

canal  leads  to  the  ring  canal  which  sur- 
rounds the  mouth  (Fig.  56).     The  ring 

canal  sends  radial  canals  into  each  ray  to  supply  the  double  row 

of  tube  feet  found  in  the  groove  at  the  lower  side  of  each  ray 

(Fig.  57).     Because  of  their  arrangement  in  rows,  the  feet  are 


Fig.  56.  —  Water  tube 
System  of  starfish. 

«/,  madreporite;   sic,  stone 
canal;  ap,  ampulla. 


3^ 


ANIMAL   BIOLOGY 


also  called   ambulacra!  feet   (Latin  ambulacra,  "forest  walks"). 

There  is  a  water  holder  {ampulla),  or  muscular  water  bulb  at  the 

base  of  each 
tube  foot  ( Fig. 
58).  These  con- 
tract and  force 
the  water  into 
the  tube  feet  and 
extend  them. 
The  cuplike 
ends  of  the 
tubes  cling  to 
the  ground  by 
suction.  The 
feet  contain 

delicate  muscles 
by  which  they 
contract  and 
shorten.  Thus 
the  animal  pulls 
itself  slowly 

along,  hundreds  of  feet  acting  together.     The  tube  feet,  for  their 

own  protection,  may  contract   and   retire  into  the   groove,   the 

water  which  extended  them  being  sent  back  into  the  ampulla. 

This  system  of  water  ^ 

vessels     (or    water-  &£ 

vascular  system)  of 

the     echinodermata 

is   characteristic    of 

them ;     i.e.     is     not 

found    elsewhere  in 

the  animal  kingdom. 

The  grooves  and  the 

plates  on  each  side 

of  them  occupy  the 


Fig.  57.  —  Starfish,  from  below;  tube  feet  extended. 


-Section  of  one  kay  and  central  portjon 
of  starfish. 
./i>  /11  f:\>  tube  feet  more  or  less  extended;    an,  eye  spot; 
k,  gills;  da,  stomach;   m,  madreporite;   st,  stone  canal; 
/,  ampulla;  ei,  ovary. 


ambulacra!  areas.  The  rows  of  spines  on  each  side  of  the  grooves 
are  freely  movable.  (What  advantage  ?)  The  spines  on  the  aboral 
surface  are  not  freely  movable. 


ECHIXODERMS   {SPINY  ANIMALS) 


37 


Respiration.  —  The  system  of  water  vessels  serves  the  additional 
purpose  of  bringing  water  containing  oxygen  into  contact  with 
various  parts  of  the  body,  and  the  starfish  was  formerly  thought 
to  have  no  special  respiratory  organs.  However  there  are  holes  in 
the  aboral  wall  through  which  the  folds  of  the  delicate  lining  mem- 
brane protrude.     These  are  now  supposed  to  be  gills  (k,  Fig.  58). 

The  nervous  system  is  so  close  to  the  aboral  surface  that  much 
of  it  is  visible  without  dissection.  Its  chief  parts  are  a  nerve  ring 
around  the  mouth,  which  sends  off  a  branch  along  each  ray. 
These  branches  may  be  seen  by  separating  the  a 

rows  of  tube  feet.     They  end  in  a  pigmented 
cell  at  the  end  of  each  ray  called  the  eye-spot. 

The  food  of  starfish  consists  of  such  animals 
as  crabs,  snails,  and  oysters.  When  the  prey 
is  too  large  to  be  taken  into  the  mouth,  the 
starfish  turns  its  stomach  inside  out  over 
the  prey  (Fig.  59).  After  the  shells  separate, 
the  stomach  is  applied  to  the  soft  digestible 
parts.  After  the  animal  is  eaten,  the  stomach 
is  retracted.  This  odd  way  of  eating  is  very 
economical  to  its  digestive  powers,  for  only 
that  part  of  the  food  which  can  be  digested  and  absorbed  is  taken 
into  the  body.  Only  the  lower  part  of  the  stomach  is  wide  and 
extensible.  The  upper  portion  (next  to  the  aboral  surface)  is 
not  so  wide.  This  portion  receives  the  secretion  from  five 
pairs  of  digestive  glands,  a  pair  of  which  is  situated  in  each  ray. 
Jaws  and  teeth  are  absent.  (Why?)  The  vent  is  sometimes 
wanting.     Why  ? 

Reproduction.  —  There  is  a  pair  of  ovaries  at  the  base  of  each 
ray  of  the  female  starfish  (Fig.  58).  The  spermaries  of  the  male 
have  the  same  position  and  form  as  the  ovaries,  but  they  are 
lighter  colored,  usually  white.1 

Regeneration  after  Mutilation.  —  If  a  starfish  loses  one  or  more 
rays,  they  are  replaced  by  growth.  Only  a  very  ignorant  oyster- 
man,  angry  at  the  depredations  of  starfish  upon  his  oyster  beds, 

1  The  sperm  cells  and  egg  cells  are  poured  out  into  the  water  by  the  adults, 
and  the  sperm  cell,  which,  like  all  sperm  cells,  has  a  vibratory,  tail-like  flagellum 
to  propel  it,_c«aches  and  fertilizes  the  egg  cell. 


Fig.  59.  —  Starfish  eat- 
ing a  sea  snail. 
b,  stomach  everted. 


33 


ANIMAL   BIOLOGY 


would  chop  starfish  to  pieces,  as  this  only  serves  to  multiply  them. 
This  power  simulates  multiplication  by  division  in  the  simplest 
animals. 

Steps  in  Advance  of  Lower  Branches.  —  The  starfish  and  other 
echinodermata  have  a  more  developed  nervous  system,  sensory 
organs,  and  digestion,  than  forms  previously  studied  ;  most  dis- 
tinctive of  all,  they  have  a  body 
cavity  distinct  from  the  food 
cavity.  The  digestive  glands, 
reproductive  glands,  and  the 
fluid  which  serves  imperfectly 
for  blood,  are  in  the  body 
cavity.  There  is  no  heart  or 
blood  vessels.  The  motions 
of  the  stomach  and  the  bend- 
ing of  the  rays  give  motion  to 
this  fluid  in  the  body  cavity. 
It  cannot  be  called  blood, 
but  it  contains  white  blood 
corpuscles. 

The  starfish  when  first 
hatched  is  an  actively  swim- 
ming bilateral  animal,  but  it  soon  becomes  starlike  (Fig.  60).  The 
limy  plates  of  the  starfish  belong  neither  to  the  outer  nor  inner 
layer  (endoderm  and  ectoderm)  of  the  body  wall,  but  to  a  third 
or  middle  layer  (mesoderm)  ;  for  echinoderms,  like  the  polyps, 
belong  to  the  three-layered  animals.  In  this  its  skeleton  differs 
from  the  shell  of  a  crawfish,  which  is  formed  by  the  hardening 
of  the  skin  itself. 

Protective  Coloration.  —  Starfish  are  brown  or  yellow.  This 
makes  them  inconspicuous  on  the  brown  rocks  or  yellow  sands 
of  the  seashore.     This  is  an  example  of  protective  coloration. 

The  Sea  Urchin 

External  Features. — What  is  the  shape  of  the  body?  What 
kind  of  symmetry  has  it?  Do  you  find  the  oral  (or  mouth)  sur- 
face? The  aboral  surface?  Where  is  the  body  flattened?  What 
is  the  shape  of  the  spines?     What  is  their  use?     How  are  the  tube 


Fig.  60.  —  Young  starfish  crawling  upon 
their  mother.     (Challenger  Reports.) 


ECHINODERMS   (SPLVY  ANIMALS) 


39 


feet  arranged?  Where  do  the  rows  begin  and  end?  Would  you 
think  a  sea  urchin  placed  upside  down  in  water,  could  right  itself 
less  or  more  readily  than  a  star- 
fish ?  What  advantage  in  turn- 
ing would  each  have  that  the 
other  would  not  have?  The 
name  sea  urchin  has  no  refer- 
ence to  a  mischievous  boy,  but 
means  sea  hedgehog  (French 
oiitsin,  hedgehog),  the  name 
being  suggested  by  its  spines. 
Comparison  of  Starfish  and 
Sea  Urchin.  —  The  water  sys- 
tem of  the  sea  urchin,  consist- 
ing of  madreporite,  tubes,  and 
water  bulbs,  or  ampullae,  is 
similar  to  that  of  the  starfish. 


Fig.6i.  — A  Sea  Urchin  crawling  up 
the  glass  front  wall  of  an  aquarium 
(showing  mouth  spines  and  tube  feet). 


The  tube  feet  and  locomotion  are  alike.  There  is  no  need  for 
well-developed  respiratory  organs  in  either  animal,  as  the  whole 
body,  inside  and  out,  is  bathed  in  water.  The  method  of  repro- 
duction is  the  same. 

The  starfish  eats  animal  food.     The  food  of  the  sea  urchin  is 
almost  exclusively  vegetable,  hence  it  needs  teeth  (Fig.  62,  63)  ; 


Fig.  62.  —  A  Sea  Urchin 
with  spines  removed, 
the  limy  plates  showing 
the  knobs  on  which  the 
spines  grew. 


Fig.  63.  —  Section  of  Sea  Urchin 
with  soft  parts  removed,  showing  the 
jaws  which  bear  the  teeth  protruding 
in  Fie.  62. 


its  food  tube  is  longer  than  that  of  a  starfish,  just  as  the  food  tube 
of  a  sheep,  whose  food  digests  slowly,  is  much  longer  than  that  of 
a  dog. 


40 


ANIMAL   BIOLOGY 


The   largest   species  of  sea   urchins   are    almost   as  big   as   a 

child's  head,  but  this  size  is  unusual.  The  spines  are  mounted 
B  on    knobs,    and    the    joint    resembles    a 

ball-and-socket  joint,  and  allow  as  wide 
range  of  movement.  Some  sea  urchins 
live  on  sandy  shores,  other  species  live 
upon  the  rocks.  The  sand  dollars  are 
lighter  colored.  (Why?)  They  are  usu- 
ally flatter  and  have  lighter,  thinner 
walls,  for  there  is  danger  of  sinking 
into  the  sand.  The  five-holed  sand 
cake  or  sand  dollar  has  its  weight  still 
further  diminished  by  the  holes,  which 
also  allow  it  to  rise  more  easily  through 
the  water.     The  flattened  lower  surface 

of  both  starfish   and  sea  urchin  causes 

the  body  to  remain  still  while  the  tube 

feet  are   stretching  forward  for  another 

step. 

Other  Echinoderms 

The  sea  cucumbers,  or  holothurians,  re- 
semble the  sea  urchin  in  many  respects, 


Fig.  64.  — The  Sea  Ot- 
ter, an  urchin  with 
mouth  (p)  and  vent  {A) 
on  same  side  of  body. 


•sSS^iil', 


Fig.  65.  —  Sea  Cucumbers. 

but  their  bodies  are  elon- 
gated, and  the  limy  plates 
very 


are  absent  or  very  mi- 
nute. The  mouth  is  sur- 
rounded by  tentacles  (Fig. 
65). 

The  brittle  stars  resem- 
ble the  starfish  in  form, 
but  their  rays  are  very 
slender,      more      distinct 

from  the  disk,  and  the  tube  feet  are  on  the  edges  of  the  rays,  not 

under  them  (Fig.  66). 


Fig.  66.  —  A  Brittle  Star. 


ECHINODERMS   {SPINY  ANIMALS} 


41 


Fig.  67.— 
Crinoid, 

arms  closed. 


The  crinoids  are  the  most  ancient  of  the  echino- 
derms.  (Figs.  67,  68.)  Their  fossils  are  very 
abundant  in  the  rocks.  They 
inhabited  the  geological 
seas,  and  it  is  believed  that 
the  other  echinoderms  de- 
scended from  them.  A  few 
now  inhabit  the  deep  seas. 
Some  species  are  fixed  by 
stems  when  young,  and  later 
break  away  and  become  free- 
swimming,  others  remain 
fixed  throughout  life. 

The  four  classes  of  the  branch  echinoderms  are 
Starfish  {asteroids),  Sea  urchins  (echincids),  Sea 
cucumbers  {holothurians),  and  Sea  lilies  {crinoids'). 

Comparative  Review 

Make  a  table  like  this  as  large  as  the  page  of  the 
notebook  will  allow,  and  fill  in  without  guessing. 


Fig.  68.—  Lusk  of  Cri- 
noid from  above, show- 
ing mouth  in  center 
and  vent  near  it,  at 
right  (arms  removed). 


Ameba 

Sponge 

Hydra 

Coral 
Polyp 

Starfish 

Is  body  round,  two- 
sided,  or  irregular 

What  organs  of  sense 

Openings  into  body 

Hard  or  supporting 
parts  of  body 

How  food  is  taken 

How  move 

How  breathe 

CHAPTER   VI 

WORMS 

/Suggestions:  —  Earthworms  may  be  found  in  the  daytime  after 
^a  heavy  rain,  or  by  digging  or  turning  over  planks,  logs,  etc.,  in 
damp  places.  They  may  be  found  on  the  surface  at  night  by 
searching  with  a  lantern.  Live  specimens  may  be  kept  in  the 
laboratory  in  a  box  packed  with  damp  (not  wet)  loam  and  dead 
leaves.  They  may  be  fed  on  bits  of  fat  meat,  cabbage,  onion, 
etc.,  dropped  on  the  surface.  When  studying  live  worms,  they 
should  be  allowed  to  crawl  on  damp  paper  or  wood.  An  earth- 
worm placed  in  a  glass  tube  with  rich,  damp  soil,  may  be  watched 
from  day  to  day. 

External  Features.  —  Is  the  body  bilateral?  Is  there  a 
dorsal  and  ventral  surface  ?  Can  you  show  this  by  a  test 
with  live  worm  ?     Do  you  know  of  an  animal  with  dorsal 

and  ventral    surface,   but  not 
bilateral  ? 

Can  you  make  out  a  head  ? 
A  head  end  ?  A  neck  ?   Touch 

FIG.  <  N  EARTHWORM.  ^     ^^     ^     ^     whether    ft 

can  be  made  to  crawl  backwards.  Which  end  is  more 
tapering  ?  Is  the  mouth  at  the  tip  of  the  head  end  or  on 
the  upper  or  lower  surface  ?  How  is  the  vent  situated  ? 
Its  shape  ?  As  the  worm  lies  on  a  horizontal  surface,  is 
the  body  anywhere  flattened  ?  Are  there  any  very  distinct 
divisions  in  the  body  ?     Do  you  see  any  eyes  ? 

Experiment  to  find  whether  the  worm  is  sensitive  (i)  to  touch, 
(2)  to  light,  (3)  to  strong  odors,  (4)  to  irritating  liquids.  Does  it 
show  a  sense  of  taste  ?     The  experiments  should  show  whether 

42 


WORMS 


43 


Fig.  70.  —  Mouth  and  Setve. 


it  avoids  or  seeks  a  bright  light,  as  a  window ;  also  whether  any 
parts  of  the  body  are  especially  sensitive  to  touch,  or  all  equally 
sensitive.  What  effect  when  a  bright  light  is  brought  suddenly  near 
it  at  night  ? 

Is  red  blood  visible  through  the  skin  ?  Can  you  notice 
any  pulsations  in  a  vessel  along  the  back  ?  Do  all  earth- 
worms have  the  same  number  of  divisions  or  rings  ?  Com- 
pare the  size  of  the  rings  or  segments.  Can  it  crawl  faster 
on  glass  or  on  paper  ? 

A  magnifying  glass  will  show  on  most  species  tiny  bristle- 
like projections  called  setce.  How  are  the  setae  arranged  ? 
(d,  Fig.  70.)  How  many  on 
one  ring  of  the  worm  ?  How 
do  they  point  ?  Does  the  worm 
feel  smoother  when  it  is  pulled 
forward    or   backward    between 

s  the  fingers  ?     Why  ?    Are  setae  on  the  lower  sur- 

face ?  Upper  surface  ?  The  sides  ?  What  is  the 
use  of  the  setae  ?  Are  they  useful  below  ground  ? 
Does  the  worm  move  at  a  uniform  rate  ?  What 
change  in  form  occurs  as  the  front  part  of  the 
body  is  pushed  forward  ?  As  the  hinder  part  is 
pulled  onward  ?  How  far  does  it  go  at  each 
movement  ?  At  certain  seasons  a  broad  band, 
or  ring,  appears,  covering  several  segments  and 
making  them  seem  enlarged  (Fig.  71).  This  is 
the  clitellum,  or  reproductive  girdle.  Is  this  girdle 
earth-     nearer  the  mouth  or  the  tail  ? 

WORM,  ^1  r  ^1 

mouth  end        Draw  the  exterior  of  an  earthworm. 

above.  Dorsal  and  Ventral  Surfaces.  —  The  earthworm 

always  crawls  with  the  same  surface  to  the  ground  ;  this 
is  called  the  ventral  surface,  the  opposite  surface  is  the 
dorsal  surface.     This  is  the  first  animal  studied  to  which 


ANIMAL   BIOLOGY 

these  terms  are  applicable.  What  are  the 
ventral  and  dorsal  surfaces  of  a  fish,  a  frog, 
a  bird,  a  horse,  a  man  ? 

The  name  "worm"  is  often  carelessly  applied 
to  various  crawling  things  in  general.  It  is  prop- 
erly applied,  however,  only  to  segmented  animals 
without  jointed  appendages. 
Although  a  caterpillar  crawls, 
it  is  not  a  worm  for  several 
reasons.  It  has  six  jointed 
legs,  and  it  is  not  a  developed 
animal,  but  only  an  early  stage 
in  the  life  of  a  moth  or  but- 
terfly. A  "  grubworm  "  also 
has  jointed  legs  (Fig.  167). 
It  does  not  remain  a  grub,  but 
in  the  adult  stage  is  a  beetle. 
A  worm  never  develops  into 
another  animal  in  the  latter 
part  of  its  life ;  its  setae  are 
not  jointed. 

The  Food  Tube.  —  The  earthworm  has 
no  teeth,  and  the  food  tube,  as  might  be 
inferred  from  the  form  of  the 
body,  is  simple  and  straight.  On 
account  of  slight  variation  in  size 
and  structure,  its  parts  are  named 
the  pharynx  (muscular),  gullet, 
crop,  gizzard  (muscular),  and  the 
long  intestine  extending  through  the  last  three 
fourths  of  its  body  (Fig.  72).  The  functions  of 
the  parts  of  the  food  tube  are  indicated  by  their 
names. 

Circulation.  —  There  is    a   large  dorsal  blood 
vessel  above  the  food  tube  (Fig.  73).     From  the 


Fig.  72.  —  Food 
TUBE  of  earth- 
worm. (Top 
view.) 


Fig.  73.  —  Food 
Tube  and 
Blood  Ves- 
sels of  earth- 
worm showing 
the  ring-like 
hearts.  (Side 
view.) 


WORMS 


45 


front  portion  of  this  tube  arise  several  large  tubular  rings 
or  "hearts"  which  are  contractile  and  serve  to  keep  the 
blood  circulating.  They  lead  to  a  ventral  vessel  below  the 
food  tube  (Fig.  74).  The  blood  is  red,  but  the  coloring 
matter  is  in  the  liquid,  not  in  the  blood  cells. 

Nervous  System.  —  Between  the  ventral  blood  vessels 
is  a  nerve  cord  composed  of  two  strands  (see  Fig.  75). 
There  is  a  slight  swelling,  or  ganglion,  on  each  strand,  in 
each  segment  (Fig.  75).  The  strands  sepa- 
rate near  the  front  end  of  the  worm,  and  a 
branch  goes  up  each  side  of  the  gullet  and 
enters  the  two  pear-shaped  cerebral  ganglia, 
or  "brain  "  (Fig.  75). 

Food.  —  The  earthworm  eats  earth  contain- 
ing organic  matter,  the  inorganic  part  passing 
through  the  vent  in  the  form  of  circular  casts 
found  in  the  morning  at  the  top  of  the  earth- 
worm's hole.     What  else  does  it  eat  ? 

The  earth  worm  needs  no  teeth,  as  it 
excretes  through  the  mouth  an  alkaline  fluid 
which  softens  and  partly  digests  the  food 
before  it  is  eaten.  When  this  fluid  is  poured  out  upon  a 
green  leaf,  the  leaf  at  once  turns  brown.  The  starch  in 
the  leaf  is  also  acted  upon.  The  snout  aids  in  pushing 
the  food  into  the  mouth. 

Kidneys.  —  Since  oxidation  is  occurring  in  its  tissues, 
and  impurities  are  forming,  there  must  be  some  way  of 
removing  impurities  from  the  tissues.  The  earthworm 
does  not  possess  one-pair  organs  like  the  kidneys  of 
higher  animals  to  serve  this  purpose,  but  it  has  numerous 
pairs  of  small  tubular  organs  called  nephridia  which  serve 
the  purpose.  Each  one  is  simply  a  tube  with  several  coils 
(Fig.  76).     There  is  a  pair  on  the  floor  of  each  segment 


Fig.  75. — 

Ganglia 
near  Mouth 

and  part  of 
nerve  chain  of 

earthworm. 


46 


AXIMAT.    BIOLOGY 


Fig.  76. —  Two  pairs 
of  Nkphridia. 


(Fig.  j6).  Each  nephridium  has  an  inner  open  end  within 
the  body  cavity,  and  its  outer  end  opens  by  a  pore  on  the 
surface  between  the  setae  (Fig.  78). 
The  nephridia  absorb  waste  water 
from  the  liquid  in  the  cclom,  or  body 
cavity  surrounding  the  food  tube, 
and  convey  it  to  the  outside. 

Respiration.  —  The  skin  of  the 
earthworm  is  moist,  and  the  blood 
capillaries  approach  so  near  to  the 
surface  of  the  body  that  the  oxygen 
is  constantly  passing  in  from  the  air,  and  carbon  dioxid 
passing  out ;  hence  it  is  constantly  breathing  through  all 
parts  of  its  skin.  //  needs  no  lungs  nor  special  respiratory 
organs  of  any  kind. 

Reproduction.  —  When  one  individual  animal  produces  both 
sperm  cells  and  egg  cells,  it  is  said  to  be  hermaphrodite.  This 
is  true  of  the  earthworm.  The  egg  cell 
is  always  fertilized,  however,  not  by  the 
sperm  cells  of  the  same  worm,  but  by 
sperm  cells  formed  by  another  worm. 
The  openings  of  these  ova  or  egg  glands 
consist  of  two  pairs  of  small  pores  found 
on  the  ventral  surface  of  the  fourteenth 
and  fifteenth  segments  in  most  species 
(see  Fig.  77).  There  are  also  two  pairs 
of  small  receptacles  for  temporarily 
holding  the  foreign  sperm  cells.  One 
pair  of  the  openings  from  these  recepta- 
cles is  found  (with  difficulty)  in  the 
wrinkle  behind  the  ninth  segment  (Fig. 
77),  and  the  other  pair  behind  the  tenth 
segment.  The  sperm  glands  are  in  front  of  the  ovaries  (Fig.  77), 
but  the  sperm  ducts  are  longer  than  the  oviducts,  and  open  behind 
them  (Figs.  77,  78).     The  worms  exchange  sperm  cells,  but  not 


Fig.  77.  —  Sperm  (sp)  and 
egg  glands  (es)  of  earth- 
worm. 


WORMS 


47 


egg  cells.  The  reproductive  girdle,  or  clitellum,  already  spoken  of, 
forms  the  case  which  is  to  hold  the  eggs  (see  Fig.  71).  When  the 
sperm  cells  have  been  exchanged,  and  the  ova  are  ready  for  fertili- 
zation, the  worm  draws  itself  backward  from  the  collarlike  case  or 
clitellum  so  that  it  slips  over  the  head.  As  it  passes  the  fifteenth 
and  sixteenth  segments,  it  collects  the  ova,  and  as  it  passes  the 
ninth  and  tenth  segments,  it  collects  the  sperm  cells 
previously  received  by  touching  another  worm.  The 
elastic,  collar-like  clitellum  closes  at  the  ends  after  it 
has  slipped  over  the  worm's  head,  forming  a  capsule. 
The  ova  are  fertilized in  this  capsule,  and  some  of  them 
hatch  into  worms  in  a  few  days.  These  devour  the 
eggs  which  do  not  hatch.  The  eggs  develop  into 
complete  but  very  small  worms  before  the  worms 
escape  from  the  capsule. 

Habits.  —  The  earthworm  is  omnivorous.  It 
will  eat  bits  of  meat  as  well  as  leaves  and  other 
vegetation.  It  has  also  the  advantage,  when 
digging  its  hole,  of  eating  the  earth  which  must 
be  excavated.  Every  one  has  noticed  the  fresh 
"casts"  piled  up  at  the  holes  in  the  morning,     fig.  78.— 

Side  view 

As  the  holes  are  partly  filled  by  rains,  the  showing  setae, 
casts  are  most  abundant  after  rains.  The 
chief  enemies  of  the  earthworm  are  moles  and 
birds.  The  worms  work  at  night  and  retire  so 
early  in  the  morning  that  it  takes  a  very  early  bird  to  catch 
a  worm.  Perhaps  the  nearest  to  an  intelligent  act  the 
earthworm  accomplishes  is  to  conceal  the  month  of  its  hole 
by  plugging  it  with  a  pebble  or  bit  of  leaf.  They  hiber- 
nate, going  below  danger  of  frost  in  winter.  In  dry  weather 
they  burrow  several  feet  deep. 

The  muscular  coat  beneath,  and  much  thicker  than  the 
skin,  consists  of  two  layers  :  an  outer  layer  runs  around  the 
body  just  beneath  the  skin,  and  an  inner,  thicker  layer  of 


nephridia 

pores,  and 

reproductive 

openings. 


48  ANIMAL    BIOLOGY 

fibers  runs  lengthwise.  The  worm  crawls  by  shortening 
the  longitudinal  muscles.  As  the  bristles  (seta)  point 
backward,  they  prevent  the  front  part  of  the  body  from 
slipping  back,  so  the  hinder  part  is  drawn  forward.  Next, 
the  circular  muscles  contract,  and  the  bristles  preventing 
the  hind  part  from  slipping  back,  the  fore  portion  is  pushed 
forward.  Is  the  worm  thicker  when  the  hinder  part  is 
being  pulled  up  or  when  the  fore  part  is  being  thrust  for- 
ward ?  Does  the  earthworm  pull  or  push  itself  along,  or 
does  it  do  both  ?  Occasionally  it  travels  backward,  e.g.  it 
sometimes  goes  backward  into  its  hole.  Then  the  bristles 
are  directed  forward. 

The  right  and  left  halves  of  the  body  are  counterparts  of 
each  other,  hence  the  earthworm  is  bilaterally  symmetrical. 
The  lungs  and  gills  of  animals  must  always  be  kept  moist. 
The  worm  cannot  live  long  in  dry  air,  for  respiration  in  the 
skin  ceases  when  it  cannot  be  kept  moist,  and  the  worm 
smothers.  Long  immersion  in  water  is  injurious  to  them, 
perhaps  because  there  is  far  less  oxygen  in  water  than  in 
the  air. 

Darwin  wrote  a  book  called  "Vegetable  Mold  and  Earth- 
worms." He  estimated  that  there  were  fifty  thousand  earth- 
worms to  the  acre  on  farm  land  in  England,  and  that  they 
bring  up  eighteen  tons  of  soil  in  an  acre  each  year.  As 
the  acids  of  the  food  tube  act  upon  the  mineral  grains  that 
pass  through  it,  the  earthworm  renders  great  aid  in  form- 
ing soil.  By  burrowing  it  makes  the  soil  more  porous  and 
brings  up  the  subsoil. 

Although  without  eyes,  the  worm  is  sensitive  to  light 
falling  upon  its  anterior  segments.  When  the  light  of  a 
lantern  suddenly  strikes  it  at  night,  it  crawls  quickly  to  its 
burrow.  Its  sense  of  touch  is  so  keen  that  it  can  detect  a 
light  puff  of  breath.     Which  of  the  foods  kept  in  a  box  of 


WORMS 


49 


damp  earth  disappeared  first?     What  is  indicated  as  to  a 

sense  of  taste  ? 

Why  is  the  bilateral  type  of  structure  better  adapted  for 

development  and  higher  organization  than  the  radiate  type 

of  the  starfish  ?     The  earthworm's  body  is  a 

double  tube  ;   the  hydra's  body  is  a  single 

tube ;  which  plan  is  more  advantageous,  and 

why  ?     Would  any  other  color  do  just  as  well 

for  an  earthworm  ?     Why,  or  why  not  ? 
The  sandworm  (Nereis)  lives  in  the  sand  of  the 

seashore,  and  swims  in  the  sea  at  night  (Fig.  79). 

It  is  more  advanced  in  structure  than  the  earth- 
worm, as  it  has  a  distinct  head  (Fig.  80),  eyes,  two 

teeth,  two  lips,  and  several  pairs  of  antennae,  and 

two  rows  of  muscular  projections  which  serve  as 

feet.     It  is  much  used  by  fishermen  for  bait.     If 

more  easily  obtained,  it  may  be  studied  instead  of 

the  earthworm. 

There  are  four  classes  in  the  branch  Vermes : 

1)  the  earthworms ;  including  sandworms  and  leeches ;  2) 
the  roundworms,  including  trichina,  hair- 
worms, and  vinegar  eels  ;  3)  flativorms, 
including  tapeworm  and  liver  fluke ;  4) 
rotifers,  which  are  mere  specks  in  size. 

The  tapeworm  is  a  flatworm  which  has  lost 
most  of  its  organs  on  account  of  its  parasitic 
life.    Its  egg  is  picked  up  by  an  herbivorous 

animal  when  grazing.     The  embryo  under- 
Fig.  80.  —  Head  . 

of  Sandworm      goes  only  partial  development  in  the  body 

(enlarged).  0£  ^g  herbivorous  animal,  e.g.  an  ox.  The 
next  stage  will  not  develop  until  the  beef  is  eaten  by  a 
carnivorous  animal,  to  whose  food  canal  it  attaches  itself 
and  soon  develops  a  long  chain  of  segments  called  a 
"tape."     Each   segment   absorbs    fluid   food   through  its 


Fig.  79.  — Sand 

Worm  x  % 

(Nereis). 


50  ANIMAL  BIOLOGY 

body  wall.  As  the  segments  at  the  older  end  mature, 
each  becomes  full  of  germs,  and  the  segments  become 
detached  and  pass  out  of  the  canal,  to  be  dropped  and 
perhaps  picked  up  by  an  herbivorous  animal  and  repeat 
the  life  cycle. 

The  trichina  is  more  dangerous  to  human  life  than  the 
tapeworm.  It  gets  into  the  food  canal  in  uncooked  pork 
(bologna  sausage,  for  example),  multiplies  there,  migrates 
into  the  muscles,  causing  great  pain,  and  encysts  there, 
remaining  until  the  death  of  the  host.  It  is  believed  to 
get  into  the  bodies  of  hogs  again  when  they  eat  rats,  which 
in  turn  have  obtained  the  cysts  from  carcasses. 

Summary  of  the  Biological  Process.  —  An  earthworm  is 
a  living  machine  which  docs  work  (digging  and  crawling; 
seizing,  swallowing,  and  digesting  food;  pumping  blood: 
growing  and  reproducing).  To  do  the  work  it  must  have 
a  continual  supply  of  energy.  The  energy  for  its  work  is 
set  free  by  the  protoplasm  (in  its  microscopic  cells)  under- 
going a  destructive  chemical  change  {oxidation).  The 
waste  products  from  the  breaking  down  of  the  protoplasm 
must  be  continually  removed  {excretion).  The  broken- 
down  protoplasm  must  be  continually  replaced  if  life  is  to 
continue  (the  income  must  exceed  the  outgo  if  the  animal 
is  still  growing).  The  microscopic  cells  construct  more 
protoplasm  out  of  food  and  oxygen  {assimilation)  supplied 
them  by  the  processes  of  nutrition  (eating,  digesting, 
breathing,  circulating).  This  protoplasm  in  turn  oxidizes 
and  releases  more  energy  to  do  work,  and  thus  the  cycle 
of  life  proceeds. 


CHAPTER   VII 

CRUSTACEANS 
Crawfish 

Suggestions.  —  In  regions  where  crawfish  are  not  found,  a  live 
crab  may  be  used.  Locomotion  and  behavior  may  be  studied  by 
providing  a  tub  of  water,  or  better,  a  large  glass  jar  such  as  a 
broad  candy  jar.  For  suggestions  on  study  of  internal  structure, 
see  p.  58. 

Habitat.  —  Do  you  often  see  crawfish,  or  crayfish,  mov- 
ing about,  even  in  water  where  they  are  known  to  be  abun- 
dant? What  does  your  answer  suggest  as  to  the  time 
when  they  are  probably  most  active  ? 

Why  do  you  never  see  one  building  its  chimney,  even 
where  crawfish  holes  are  abundant?  Is  the  chimney 
always  of  the  same  color  as  the  surface  soil?  Are  the 
crawfish  holes  only  of  use  for  protection  ?  In  what  kind 
of  spots  are  crawfish  holes  always  dug  ?  Why  ?  What 
becomes  of  crawfish  when  the  pond  or  creek  dries  up  ? 
How  deep  are  the  holes  ?  How  large  are  the  lumps  of 
mud  of  which  the  chimney  is  built?  How  does  it  get 
them  out  of  the  hole  ?  Why  is  the  mud  built  into  a  chim- 
ney instead  of  thrown  away  ?  (What  would  happen  to  a 
well  with  its  mouth  no  higher  than  the  ground?)  Why 
are  crawfish  scarce  in  rocky  regions,  as  New  England  ? 

How  does  the  color  of  the  crawfish  compare  with  its 
surroundings  ?  Is  its  color  suited  to  life  in  clear  or  muddy 
water  ?     Define  protective  coloration. 

51 


52  ANIMAL  BIOLOGY 

Habits.  —  Does  the  crawfish  walk  better  in  water  or  out 
of  it  ?  Why  ?  Does  it  use  the  legs  with  the  large  claws 
to  assist  in  walking?  Do  the  swimmerets  (under  the  ab- 
domen) move  fast  or  slow  ?  (Observe  it  from  below  in  a 
large  jar  of  clear  water.)  What  propels  it  backward? 
Forward  ?  Does  the  crawfish  move  at  a  more  uniform 
rate  when  swimming  backward  or  forward  ?  Why  ?  In 
which  way  can  it  swim  more  rapidly  ?  Do  the  big  legs 
with  claws  offer  more  resistance  to  the  water  while  it  is 
swimming  backward  or  forward  ?  How  does  it  hold  the 
tail  after  the  stroke,  while  it  is  darting  backward  through 
the  water?  Hold  a  crawfish  with  its  tail  submerged  and 
its  head  up.  Can  the  tail  strike  the  water  with  much 
force  ?  Allow  it  to  grasp  a  pencil :  can  it  sustain  its  own 
weight  by  its  grip  ? 

Feeding. —  Offer  several  kinds  of  food  to  a  crawfish  that 
has  not  been  alarmed  or  teased.  Does  it  prefer  bread, 
meat,  or  vegetables  ?  How  does  it  get  the  food  to  its  mouth? 
Does  it  eat  rapidly  or  slowly  ?  Does  it  tear  the  food  with 
the  big  pincers  ?  Can  it  gnaw  with  the  small  appendages 
near  the  mouth  ? 

Breathing.  —  Does  the  crawfish  breathe  with  gills  or 
lungs  ?  Place  a  few  drops  of  ink  near  the  base  of  the  hind 
legs  of  a  crawfish  resting  quietly  in  shallow  water.  Where 
is  the  ink  drawn  in  ?  Where  does  it  come  out  ?  To  ex- 
plain the  cause  and  purpose  of  this  motion,  place  a  craw- 
fish in  a  large  glass  jar  containing  water,  and  see  the 
vibratory  motion  of  the  parts  under  the  front  portion  of 
the  body.  There  is  a  gill  paddle,  or  gill  bailer,  under  the 
shell  on  each  side  of  the  body  that  moves  at  the  same  rate. 

Senses.  —  Crawfish  are  best  caught  with  a  piece  of  meat 
or  beef's  liver  tied  to  a  string.  Do  they  always  lose  hold 
as  soon  as  they  are  lifted  above  the  water  ?     What  do  you 


CRUSTACEA. NS 


53 


conclude  as  to  the  alertness  of  their  senses  ?  Does  the  cov- 
ering of  its  body  suggest  the  possession  of  a  delicate  or  dull 
sense  of  touch  ? 

Of  what  motions  are  the  eyes  capable?  Touch  one  of 
the  eyes.  The  result  ?  Can  a  crawfish  see  in  all  direc- 
tions ?  To  test  this,  place  a  crawfish  on  a  table  and  try 
whether  you  can  move  to  a  place  where  you  can  see  the 


Fig.  8i.  — Crawfish 
(dorsal  surface). 


FIG.  82. 


crawfish  without  seeing  its  eyes.  What  are  the  advantages 
and  disadvantages  of  having  the  eyes  on  stalks  ? 

Touch  the  body  and  the  several  appendages  of  the 
crawfish.  Where  does  it  seem  most  sensitive  to  touch  ? 
Which  can  reach  farther,  the  antennae  or  the  big  claws? 
Why  are  short  feelers  needed  as  well  as  long  ones  ? 

Make  a  loud  and  sudden  noise  without  jarring  the  craw- 
fish.    Is  it  affected  by  sound? 

External  Anatomy  (Figs.  81,  82,  83,  84).  —  Is  the  body  of 
the  crawfish  rounded  out  (convex)  everywhere,  or  is  any 
part  of  its  surface  either  flat  or  rounded  in   (concave)  ? 


54 


ANIMAL   BIOLOGY 


What  color  has  the  crawfish  ?  Is  this  color  of  any  use  to 
the  crawfish  ? 

Make  out  the  two  distinct  regions  or  divisions  of  the  body 
(Fig.  81).  The  anterior  (front)  region  is  called  the  head- 
chest  or  cephalothorax,  and  the  posterior  (rear)  region  is 

called  the  tail. 
Which  region  is 
larger  ?  Why  ? 
Which  is  flex- 
ible ?  Why  ? 
Is  the  covering 

of  the  body  hard 
Fig.  83.— Lateral  view  of  Crawfish.  r    .       „T1 

or    soft  ?      What 

is  the  advantage  of  such  a  covering  ?  What  are  its  dis- 
advantages ?  How  is  the  covering  modified  at  the  joints 
to  permit  motion  ? 

Tail.  —  How  many  joints,  or  segments,  on  the  tail  ?  (Figs. 
81,  83.)  Does  the  hard  covering  of  each  segment  slip 
under  or  over  the  segment  behind  it  when 
the  abdomen  is  straight  ?  Does  this  lessen 
friction  while  swimming  forward  ? 

Is  there  a  pair  of  sivimmercts  to  each 
segment  of  the  abdomen?  (Figs.  82,  86.) 
Notice  that  each  swimmeret  has  a  main 
stalk  (protopod),  an  outer  branch  (exopod), 
and  an  inner  branch  (endopod)  (Fig.  84). 
Are  the  stalk  and  the  branches  each  in 
one  piece  or  jointed  ?  The  middle  part  of  the  tail  fin  is 
called  the  telson.  By  finding  the  position  of  the  vent, 
decide  whether  the  food  tube  goes  into  the  telson 
(Fig.  82).  Should  it  be  called  an  abdominal  segment. 
Are  the  side  pieces  of  the  tail  fin  attached  to  the  telson 
or  to  the  sixth  segment  ?     Do  these  side  pieces  correspond 


Fig.  84. — 
Fourth  Abdo- 
minal Segment 
of  Crawfish 
with  swimmeret. 


CRUSTACEANS 


55 


to    swimmerets  ?      Do    they    likewise    have    the   Y-shaped 

structure  ?    (Fig.  86.) 

If  the  swimmerets  on  the  first  abdominal  segment  are 

large,  the  specimen  is  a  male.     If  they  are  small,  it  is  a 

female.     Which  sex  is  shown  in  Fig.  82  ? 

Fig.  86  ? 

Carapace.  —  The   covering  of   the  head 

chest  (cephalothorax)  is  called   the   cara- 
pace.    Has  it  free  edges  ?     The  gills  are 

on  the  sides  of  the  body  and  are  covered 

by  the  carapace  (Fig.  87).     The  projection 

in  front  is  called  the  rostrum,  meaning  beak. 

Does  the  rostrum  project  beyond  the  eyes  ? 

There  is  a  transverse  groove  across  the  cara- 
pace which  may 
be  said  to  divide 
the  head  from  the 
abdomen.  Where 
does  this  groove  end  at  the  sides  ? 
Legs.  —  How  many  legs  has  the 
crawfish  ?  How  many  are  provided 
with  large  claws  ?  Small  claws  ? 
Is  the  outer  claw  hinged  in  each 


Fin. 85 


ble;  2, 3, maxillae; 
4,5,6,maxillipeds. 


pincers 


Fig.  86.  —  Crawfish 

(ventral  surface). 


of    the    large    graspin 
The  inner  claw  ? 

Appendages  for  Taking  Food.  — 
If  possible  to  watch  a  living  craw- 
fish eating,  notice  whether  it  places 
the  food  directly  into  the  mouth  with  the  large  claws.  Bend 
the  large  claws  under  and  see  if  they  will  reach  the  mouth. 
Attached  just  in  front  of  the  legs  the  crawfish  has  three 
pairs  of  finger-like  appendages,  called  foot  jaws(maxilli- 
peds),  with  which  it  passes  the  food  from  the  large  pincers 


56 


ANIMAL   BIOLOGY 


to  its  mouth  (Figs.  85,  86).     They  are  in  form  and  use  more 
like  ringers  than  feet.     In  front  of  the  foot  jaws  are  two 

pairs  of  thin  jaws 
(maxillae)  and  in 
front  of  the  thin 
jaws  are  a  pair  of 
stout  jaws  (mandi- 
bles) (Fig.  85).  Do 
the  jaws  move 
sidewise  or  up 
and  down  ?  Which 
of  the  jaws  has  a 
jointed  finger  (palp)  attached  to  it  ?  Do  all  of  the  appen- 
dages for  taking  food  have  both  exopod  and  endopod 
branches  on  a  basal  stalk  or  protopod  ?  Which  of  the 
appendages  have  a  scalloped  edge?  How  would  you  know 
from  looking  at  the  crawfish  that  it  is  not  merely  a 
scavenger  ?    Why  are  there  no  pincers  on  the  hind  feet  ? 

Sense  Organs.  —  Find  the  antenna,  or  long  feelers  (Figs. 
82,  90).  Are  the  antennae  attached  above  or  below  the 
eyes  ?     (Fig.  87.) 


Fig.  87. 


Gill  cover  removed  and  gills  exposed. 
Mp,  gill  bailer. 


Lengthwise  Section  of  Male  Crawfish. 


c,  heart;   A c,  artery  to  head;   Aa,  artery  to  abdomen;   Km,  stomach;    D,  intestine; 
Lt  liver;    T,  spermary;   Go,  opening  of  sperm  duct;   G,  brain;  N,  nerve  chain. 

Find  the  pair  of  antennules,  or  small  feelers.  Are  their 
divisions  like  or  unlike  each  other  ?  Compare  the  length 
of  the  antennules  and  the  antennas.  Compare  the  flex- 
ibility of  the  antennae  with  that  of  the  other  appendages. 


CRUSTACEAXS  $7 

Observe  the  position  of  the  eyes  (Figs.  81,  88).  How  long 
are  the  eyestaiks  ?  Is  the  stalk  flexible  or  stiff  ?  Touch  the 
eye.  Where  is  the  joint  which  enables  the  stalk  to  move  ? 
Is  the  outer  covering  of  the  eye  hard  or  soft  ?  A  mounted 
preparation  of  the  transparent  covering  (cornea)  of  the 
eye,  seen  with  lower  power  of  microscope,  reveals  that  the 
cornea  is  made  up  of  many  divisions,  called  facets.  Each 
facet  is  the  front  of  a  very  small  eye,  hundreds  of  which 
make  up  the  whole  eye,  which  is  therefore  called  a  com- 
pound eye.  The  elongated  openings  to  the  ear  sacs  are 
located  each  on  the  upper  side  of  the  base  of  a  small  feeler 
just  below  the  eye. 

Respiratory  System.  —  The  respiratory  organs  are  gills 
located  on  each  side  of  the  thorax  in  a  space  between  the 
carapace  and  body  (Fig.  87).  The  gills  are  white,  curved, 
and  feathery.  Is  the  front  gill  the  largest  or  the  smallest  ? 
The  gills  overlap  each  other ;  which  is  the  outermost  gill  ? 
On  the  second  maxilla  is  a  thin,  doubly  curved  plate  called 
a  gill  bailer  (Fig.  85).  The  second  maxilla  is  so  placed 
that  the  gill  bailer  comes  at  the  front  end  of  the  gill 
chamber.  The  bailer  paddles  continually,  bringing  the 
water  forward  out  of  the  gill.  The  gills  are  attached 
below  at  the  base  of  the  legs.  Are  the  gills  thick  or  thin  ? 
How  far  upward  do  they  go  ?  Does  the  backward  motion 
in  swimming  aid  or  hinder  the  passage  of  the  water  through 
the  gills  ?  Does  a  crawfish,  when  at  rest  on  the  bottom 
of  a  stream,  have  its  head  up  or  down  stream  ?  Why? 

Openings. — The  slitlike  vent  is  on  the  under  side  of 
the  telson  (Figs.  82,  88).  The  mouth  is  on  the  under  side 
of  the  thorax  behind  the  mandibles.  At  the  base  of  the 
long  antennae  are  the  openings  from  the  green  glands,  two 
glands  in  the  head  which  serve  as  kidneys  (Fig.  89). 
The  openings  of  the  reproductive  organs  are  on  the  third 


58 


AX /.UAL   BIOLOGY 


/:'V.  'V;;:-; 


pair  of  legs  in  the  female,  and  the  fifth 
pair  of  legs  in  the  male  (Fig.  88).  The 
eggs  are  carried  on  the  swimmerets. 

Internal  Structure.  —  Suggestions.  If 
studied  by  dissection,  it  will  be  necessary 
to  have  several  crawfish  for  each  pupil,  one 
for  gaining  general  knowledge,  and  others  for 
studying  the  systems  in  detail.  Specimens 
should  have  lain  in  alcohol  for  several  days. 

The  Food  Tube.  —  Is  the  stomach  in  the 
head  portion  of  the  cephalothorax  or  in  the 
thoracic  portion?  ( Figs.  88,  89).  Is  the  stomach 
large  or  small?  What  is  its  general  shape? 
Does  the  gullet  lead  upward  or  backward? 
Is  it  long  or  short?  (Fig.  88.)  The  mid  tube, 
which  is  the  next  portion  of  the  food  tube,  is 
smaller  than  the  stomach.  On  each  side  of 
Fig.  89. —  Level  length-    jt  are  openings   from   the   bile  ducts  which 

wise  section  showing        .     .  .  r  ,        ..  ,        . 

bring  the  secretion  from  the  digestive  gland, 
sometimes  called  the  liver.  Does  this  gland 
extend  the  whole  length  of  the  thorax?  Is 
it  near  the  floor  or  the  top  of  the  cavity? 
The  third  and  last  portion  of  the  food  tube 
is  the  intestine.     It  extends  from  the  thorax 

to  the  vent.     Is  it  large 

or    small?     Straight    or 

curved?     The  powerful 

flexor  muscles  of  the  tail 

lie  in  the  abdomen  below 

the  intestines.  Compare 

the  size  of  these  muscles 

with  the  extensor  muscle 

above  the  intestine  (Fig. 

90).  Why  this  difference? 

Does  the  food  tube  ex- 
tend into  the  telson  ?  Do- 
Fig.  90.  —  Section  of  Crawfish  showing 

Cate  the  vent  (Fig.  90).  stomach  s,  liver  /*,  and  vent  a. 


A,  heart. 
d,  green  gland. 
le,  liver. 
kie ,  gills. 
kit,  gill  cavity. 
}>ia,  stomach. 
(After  Huxley.) 


CRUSTACEANS 


59 


The  Circulation. — The  blood  is  a  liquid  containing  white  cor- 
puscles.    It  lacks  red  corpuscles  and  is  colorless.     The  heart  is  in 

the  upper  part  of  the   thorax.     It  is  sur- 
rounded by  a  large,  thin  bag,  and  thus  it  is 

in  a  chamber  (called  the  pericardial  sinus). 

The  blood  from  the  pulmonary  veins  enters 

-this  sinus  before  it  enters  the  heart.     The 

origin  of  this  pericardial  sinus  by  the  fusing  of 

veins  is  shown  in  Fig.  1 30.     Does  one  artery, 

or  do  several  arteries,  leave  the  heart  ?   There 

is  a  larger  dorsal  artery  lying  on  the  intestine 

and  passing  back  to  the  telson ;  there  are 

three  arteries  passing  forward  close  to  the 

dorsal  surface  (Figs.  89, 91).   One  large  artery 

(the  sternal)  passes  directly  downward  (Figs. 

88,  91),  and  sends  a  branch   forward  and 

another  backward  near  the  ventral  surface. 

The  openings  into  the  heart  from  the  sinus 

have  valvular  lips  which  prevent  a  backward 

flow  of  blood  into  the  sinus.     Hence,  when 

the  heart  contracts,  the  blood  is  sent  out  into  the  sev- 
eral arteries.  The  arteries  take  a  supply  of  fresh  blood 
to  the  eyes,  stomach,  muscles,  liver,  and  the  various 
organs.  After  it  has  given  oxygen  to  the  several  organs 
and  taken  up  carbon  dioxid,  it  returns  by  veins  to  pass 
through  the  gills  on  each  side,  where  it  gives  out  the  use- 
less gas  and  takes  up  oxygen  from  the  water.  It  is  then 
led  upward  by  veins  into  the  pericardial  sinus  again. 
A  double  nerve  chain  of  ganglia  supplies  nerve 
force  to  the  various  nerves  (Fig.  92).  This  main 
nerve  chain  lies  along  the  ventral  surface  below  the 
food  tube  (Fig.  90),  except  one  pair  of  ganglia  which 
lie  above  the  esophagus  or  gullet  (Fig.  88),  and  are 
Fig.  92.         called  the  supra-esophageal  ganglia,  or  brain. 

Crustacea.  —  Because  of  the  limy  crust  which  covers 
the  crawfish  and  its  kindred,  they  are  placed  in  the  class 
called  Crustacea. 


Fig.  91.  —  Showing  heart 
and  main  blood  vessels. 


6o 


ANIMAL   BIOLOGY 


Fig.  93.  —  Crab  from 
below. 


Fig.  94. —  Hermit  Crab, 
using  shell  of  sea  snail 
lor  a  house. 


Decapods.  —  All  Crustacea  which  have   ten  feet  belong 
in   the   order    called  decap'oda  (ten-footed).      This  order 
includes  the  crabs,  lobsters,  shrimp, 
i  .*«faraS*%)|J  etc.     The  crabs  and  lobsters  are  of 

considerable  importance  because  of 
use  as  food.  Small  boys  sometimes 
catch  crawfish,  and  in  some  instances 
are  known  to  cook  and  eat  them  for 
amusement, 
the  only  part  cooked  being  the 
muscular  tail.  The  crab's  tail  is 
small  and  flat  and  held  under  the 
body  (Fig.  93). 

Since  the  limy  covering  to  serve 
the  purpose  of  protection  is  not 
soft  enough  to  be  alive  and  growing,  it  is  evident  that  the 
Crustacea  are  hampered  in  their  growth  by  their  crusty 

covering.  Dur- 
ing the  first 
year  the  craw- 
fish sheds  its 
covering,  or 
molts  three 
times,  and 

once  each  year 
thereafter.  It 
grows  very  fast 
for  a  few  days 
just  after  molt- 
ing, while  the 
Fig.  95. —  Development  of  a  Crab.  covering  is  soft 

a,  naupliusjust  after  hatching;  b,c,d,  zoea;   e,  megalops;  _/,  adult.        and  extensible 

Question:   Which   stage   is  most   like   a  crayfish?    Compare 
with  metamorphoses  of  insects.  OinCe     It     IS     3.1 


CRUSTACEANS  6 1 

the  mercy  of  birds,  fish,  and  other  enemies  while  in  this 
soft  and  defenseless  condition,  it  stays  hidden  until  the 
covering  hardens.  Hence  it  cannot  eat  much,  but  probably 
by  the  absorption  of  water  the  tissues  grow ;  that  is,  enlarge. 
In  the  intervening  periods,  when  growth  is  impossible,  it 
develops  ;  that  is,  the  tissues  and  organs  change  in  structure 
and  become  stronger.  "  Soft-shelled  crab  "  is  a  popular  dish, 
but  there  is  no  species  by  that  name,  this  being  only  a  crab 
just  after  molting  which  has  been  found  by  fishermen  in 
spite  of  its  hiding. 

General  Questions.  —  How  do  crawfish  choose  their  food  ? 
How  long  can  they  live  out  of  water?  Why  do  their  gills  remain 
moist  out  of  water  longer  than  a  fish?  How  do  they  breathe 
out  of  water?  Are  they  courageous  or  cowardly  animals?  When 
they  lose  appendages  when  fighting  or  molting,  they  are  readily 
reproduced,  but  the  part  molts  several  times  in  regaining  its 
size.  Have  you  seen  crawfish  with  one  claw  smaller  than  the 
other?     Explain. 

Compare  the  crawfish  and  crab  (Figs.  81,  93,  and  95)  in  the 
following  particulars  :  shape,  body,  eyes,  legs,  abdomen,  habitat, 
movement. 

KEY   TO   THE  FOUR  CLASSES  IN  BRANCH  ARTHROPODS 

1 .  Insects    ...  3  body  divisions,  6  legs 

2.  Arachnids   .     .  2  body  divisions.  8  legs 

3.  Myriapods  .     .  many  body  divisions,  many  legs 

4.  Crustaceans    .  gill  breathers,  skeleton  (external)  limy 

By  the  aid  of  the  key  and  of  figures  96-105,  classify  the  following 
Arthropods :  tick,  thousand-leg  centipede,  king  crab,  pill  bug,  spider 
scorpion,  beetle. 


62 


A  XI MA  I.    BIOLOGY 


Fig.  96.  — Pill 
Bug. 


Fig.  98.  —  Scorpion. 


€f 


Fig.  ioi.  —  One  Seg- 
ment of  Centipede 
with  one  pair  of  legs. 


; 

1— -  2 

I 

Fig.  102.— 
One  Segment 

of  Thousand 
Legs  with  two 
pairs  of  legs. 


a 

Fig.  99.  • 
before  and  after 
feeding. 

!      '  v,to  \    k/JL 


Fig.  103.  —  Thousand 
Legs. 


Fig.  104.  — A  Spider.  Fig.  105.  — King  Crab. 

Illustrated  Study.    Classification  of  Arthropods.    Key  on  p.  61. 


CHAPTER   VIII 

INSECTS 

The  Grasshopper 

Suggestions.  —  Collect  grasshoppers,  both  young  and  full- 
grown,  and  keep  alive  in  broad  bottles  or  tumblers  and  feed  on 
fresh  grass  or  lettuce.  When  handling  a  live  grasshopper,  never 
hold  it  by  its  legs,  as  the  joints  are  weak.  To  keep  them  for 
some  time  and  observe  their  molts,  place  sod  in  the  bottom  of  a 
box  and  cover  the  box  with  mosquito  netting  or  wire  gauze. 

What    is  the   general   shape  of   its  body?     (Fig.    106.) 
Where  is  the  body  thickest?     Is  it  bilaterally  symmetri-     ^ 
cal,  that  is,  are  the  two  sides  of  the 
body  alike  ?    Is  the  skeleton,  or  hard 
part  of  the  body,  internal  or  external  ? 
Is    the    skeleton    as    stiff    and   thick 
as  that  of  a  crawfish  ?     What  is  the        fig.  106.  —  a  grass- 
length  of  your  specimen  ?     Its  color?  hopper. 

Why  does  it  have  this  coloration  ?     In  what  ways  does  the 
grasshopper  resemble  the  crawfish  ?     Differ  from  it  ? 

The  Three  Regions  of  the  Body.  —  The  body  of  the  grass- 
hopper is  divided  into  three  regions,  — the  head,  thorax,  and 
abdomen.  Which  of  these  three  divisions  has  no  distinct 
subdivisions  ?  The  body  of  the  grasshopper,  like  that  of 
the  earthworm,  is  made  of  ringlike  segments.  Are  the 
segments  most  distinct  in  the  head,  thorax,  or  abdomen? 
Which  region  is  longest  ?  Shortest  ?  Strongest  ?  Why  ? 
Which  region  bears  the  chief  sense  organs  ?  The  ap- 
pendages for  taking  food  ?  The  locomotory  appendages  ? 
Which  division  of  the  body  is  most  active  in  breathing  ? 

63 


64 


ANIMAL   BIOLOGY 


~^$C 


The  Abdomen.  —  About  how  many  segments  or  rings  in 
the  abdomen  ?  Do  all  grasshoppers  have  the  same  num- 
ber of  rings  ?  (Answer  for  different  species  and  different 
individuals  of  the  same  species.)  The  first  segment  and 
the  last  two  are  incomplete  rings.  Does  the  flexibility  of 
the  abdomen  reside  in  the  rings,  or  the  joints  between  the 
rings  ?  Is  there  merely  a  thin,  soft  line  between  the  rings, 
or  is  there  a  fold  of  the  covering  ?  Does  one  ring  slip  into 
the  ring  before  it  or  behind  it  when  the  abdomen  is  bent  ? 
As  the  grasshopper  breathes,  does  each  ring  enlarge 
and  diminish  in  size  ?  Each  ring  is  divided  into  two  parts 
by  folds.  Does  the  upper  half-ring 
overlap  the  lower  half-ring,  or  the 
reverse  ?  With  magnifying  glass,  find 
a  small  slit,  called  a  spiracle,  or  breath- 
ing hole,  on  each  side  of  each  ring  just 
above  the  side  groove  (Fig.  106).  A 
tube  leads  from  each  spiracle.  While 
the  air  is  being  taken  in,  do  the  two 
portions  of  the  rings  move  farther 
apart  ?  When  they  are  brought 
together  again,  what  must  be  the 
effect  ?  In  pumping  the  air,  the  abdomen  may  be  said  to 
work  like  a  bellows.  Bellows  usually  have  folds  to  allow 
motion.     Is  the  comparison  correct? 

How  many  times  in  a  minute  does  the  grasshopper  take 
in  air?  If  it  is  made  to  hop  vigorously  around  the  room 
and  the  breathing  is  again  timed,  is  there  any  change  ? 

Find  the  ears  on  the  front  wall  of  the  first  abdominal 
ring  (Fig.  107).  They  may  be  seen  by  slightly  pressing 
the  abdomen  so  as  to  widen  the  chink  between  it  and 
the  thorax.  The  ears  are  merely  glistening,  transparent 
membranes,  oval  in  form.     A  nerve  leads  from  the  inner 


Fiu.  107.  —  A  Grass- 
hopper Dissected. 


r    blunt    points 

are 

1VJL, 

??p 

*£- 

INSECTS  65 

surface  of  each  membrane.  State  any  advantage  or  dis- 
advantage in  having  the  ears  located  where  they  are. 

Ovipositor.  — ■  If  the  specimen  is  a  female,  it  has  an  egg- 
placer  or  ovipositor,  consisting  of  four  blunt  projections  at 
the  end  of  the  abdomen  (Fig.  107).  If  it  is  a  male, 
there  are  only  two  appendages.  These  are  above  the 
end  of  the  abdomen,  and  smaller  than  the  parts  of  the 
ovipositor.  Females  are  larger  and  more  abundant  than 
males.  In  laying  the  eggs,  the  f 
brought  tightly  together  and  then 
forced  into  the  ground  and  opened 
(Fig.  108).  By  repeating  this,  a  pit 
is  made  almost  as  deep  as  the  abdo- 
men is  long.  What  sex  is  shown  in 
Fig.  106  ?     Fig.  107  ? 

Draw  a  side  view  of  the  grass- 
hopper. 

Thorax.  —  This,  the  middle  por-  fig.  108.  — grasshopper 
tion  of  the  body,  consists  of  tJiree 

segments  or  rings  (Fig.  107).  Is  the  division  between  the 
rings  most  apparent  above  or  below  ?  Which  two  of  the 
three  rings  are  more  closely  united  ? 

The  front  ring  {^ro  thorax)  of  the  thorax  has  no  rings. 
Is  it  larger  above  or  below  ?  Does  it  look  more  like  a 
collar  or  a  cape  ?  (Fig.  106.)  A  spiracle  is  found  on  the 
second  ring  {mesothorax,  or  middle  thorax)  just  above  the 
second  pair  of  legs.  There  is  another  in  the  soft  skin 
between  the  prothorax  and  mesothorax  just  under  the 
large  cape  or  collar.  The  last  ring  of  the  thorax  is  called 
the  metathorax  (rear  thorax). 

How  many  legs  are  attached  to  each  ring  of  the  tho- 
rax ?  Can  a  grasshopper  walk?  Run?  Climb?  Jump? 
Fly?     Do  any  of  the  legs  set  forward?     (See  Fig.   106.) 

F 


- 


66 


ANIMAL   BIOLOGY 


Outward  ?  Backward  ?  Can  you  give  reasons  for  the  posi- 
tion of  each  pair?  (Suggestion:  What  is  the  use  of  each 
pair?)  If  an  organ  is  modified  so  that  it  is  suited  to  serve 
some  particular  purpose  or  function,  it  is  said  to  be  special- 
ized. Are  any  of  the  legs  specialized  so  that  they  serve 
for  a  different  purpose  than  the  other  legs  ? 

The  leg  of  a  grasshopper  (as  of  all  insects)  is  said  to 
have  Jive  parts,  all  the  small  parts  after  the  first  four  parts 
being  counted  as  one  part  and  called  the  foot.  Are  all 
the  legs  similar,  that  is,  do  the  short  and  long  joints  in  all 
come  in  the  same  order  ?     Numbered  in  order  from  the 


Fig.  109.  —  How  a  Grasshopper 
Walks. 


Fig.  iio.  —  How  a  Spider 
Walks. 


body,  which  joint  of  the  leg  is  the  largest,  —  the  first,  sec- 
ond, third,  or  fourth  ?  Which  joint  is  the  shortest  ?  The 
slenderest?  Which  joint  has  a  number  of  sharp  points  or 
spines  on  it  ?  Find  by  experiment  whether  these  spines 
are  of  use  in  walking  (Fig.  106).  Jumping?  Climbing? 
In  what  order  are  the  legs  used  in  walking  ?  How  many 
legs  support  the  body  at  each  step  ? 

All  animals  that  have  ears  have  ways  of  communicating 
by  sounds.  Why  would  it  be  impossible  for  the  grasshop- 
per to  have  a  voice,  even  if  it  had  vocal  cords  in  its 
throat  ?  The  male  grasshoppers  of  many  species  make  a 
chirping,  or  stridulation,  by  rubbing  the  wing  against  the 
leg.     Look  on  the  inner  side  (why  not  outer  side  ?)  of  the 


IXSECTS 


67 


used 


Fig.  iii.- 
Spines, 
chirping. 

B,  the  same  more  enlarged. 


largest  joint  of  the  hind  leg  for  a  row  of  small  spines  visi- 
ble with  the  aid  of  a  hand  lens  (Fig.  in).  The  sound  is 
produced  by  the  outer  wings  rubbing  against  the  spines. 
Have  you  noticed  whether  the  sound  is 
produced  while  the  insect  is  still  or  in 
motion  ?  Why  ?  The  male  grasshop- 
pers of  some  species,  instead  of  having 
spines,  rub  the  under  side  of  the  front 
wing  on  the  upper  side  of  the  hind  wing. 
Wings.  —  To  what  is  the  first  pair 
of  wings  attached  ?  The  second  pair  ? 
Why  are  the  wings  not  attached  to  the 
prothorax  ?  Why  are  the  wings  attached 
so  near  the  dorsal  line  of  the  body  ?  Why  are  the  second 
and  third  rings  of  the  thorax  more  solidly  joined  than  the 
first  and  second  rings  ? 

Compare  the  first  and  second  pairs  of  wings  in  shape, 
size,  color,  thickness,  and  use  (Fig.   112).     How  are  the 

second  wings  folded  so  as  to  go 
under  the  first  wings  ?  About 
how  many  folds  in  each  ? 
Draw  a  hind  wing  opened  out. 
Head.  —  What  is  the  shape  of 
the  head  viewed  from  the  front,  the 
side,  and  above  ?  Make  sketches. 
What  can  you  say  of  a  neck  ?  Is 
the  head  movable  in  all  directions  ? 
What  is  the  position  of  the  large 
eyes  ?  Like  the  eyes  of  the  craw- 
fish, they  are  compound,  with  many  facets.  But  the  grass- 
hopper has  also  three  simple  eyes,  situated  one  in  the  middle 
of  the  forehead  and  one  just  above  each  antenna.  They 
are  too  small  to  be  seen  without  a  hand  lens.     How  does 


Fig.  112. 


—  Grasshopper  in 
Flight. 


68 


ANIMAL  BIOLOGY 


the  grasshopper's  range  of  vision  compare  with  that  of  the 
crawfish  ? 

Are  the  antennae  flexible  ?  What  is  their  shape  ?  Posi- 
tion ?  Are  they  segmented  ?  Touch  an  antenna,  a  wing, 
a  leg,  and  the  abdomen  in  succession.  Which  seems  to  be 
the  most  sensitive  to  touch  ?  The  antennas 
are  for  feeling  ;  in  some  species  of  insects  they 
are  also  the  organs  of  hearins:. 

The  mouth  parts  of  a  grasshopper  are  highly 
specialized.  They  should  be  compared  with 
the  mouth  parts  of  a  beetle  shown  in  Fig.  113, 
since  the  mouth  parts  of  these  two  insects 
correspond  closely.  If  the  grasshopper  is  fed  with  a  blade 
of  fresh  grass,  the  function  of  each  mouth  part  may  be 
plainly  seen.  It  is  almost  impossible  to  understand  these 
functions  by  studying  a  dead  specimen,  but  a  fresh  speci- 
men is  much  better  than  a  dry  one. 

The  upper  lip,  or  labrum,  is  seen  in  front.  Is  it  tapering 
or  expanded  ?  In  what  direction  is  it  movable  ?  The  dark 
pointed  biting  jaws  {mandibles)  are  next.     Are  they  curved 


Fig.  113. 


Fig.  114.  —  a.  Food  Tube  of  Beetle. 

b,  gizzard;  d,  intestine;  c,  biliary  vessels.     See  Fig.  127. 

or  straight  ?  Sharp  or  blunt  pointed  ?  Notched  or  smooth  ? 
Do  they  work  up  and  down,  or  sideways  ?  The  holding  jaws 
{maxilla),  each  with  two  jaw  fingers  (maxillary  palpi)  are 
behind  the  chewing  jaws.  Why  ?  The  lower  lip  (labium) 
has  a  pair  of  lip  fingers  (labial palpi)  upon  it.     The  brown 


INSECTS  69 

tongue,  usually  bathed  in  saliva,  is  seen  in  the  lower  part  of 
the  mouth.  Since  the  grasshopper  has  no  lips,  or  any  way 
of  producing  suction,  it  must  lap  the  dew  in  drinking.  Does 
it  merely  break  off  bits  of  a  grass  blade,  or  does  it  chew  ? 

The  heart,  circulation,  nervous  system,  digestive  and  res- 
piratory organs  of  the  grasshopper  agree  mainly  with  the 
general  description  of  the  organs  of  insects  given  in  the 
next  section. 

Microscopic  Objects.  —  These  may  be  bought  ready 
mounted,  or  may  be  examined  fresh.  A  portion  of  the 
covering  of  the  large  eye  may  be  cut  off  and  the  dark  layer 
on  the  inside  of  the  covering  scraped  off  to  make  it  trans- 
parent. What  is  the  shape  of  the  facets  ?  Can  you  make 
any    estimate    of 

their  number?    A  J*         eJkf       Imfa®     J^^Cw 

portion      of     the  -^ c,   ^'cia'~*  / 

transparent    hind        Z  P\^sSLr§(        F~~ir^H^0^K_ffi) 
wing  may  be  used,      ^\±£sxM^?        ^^^^^^f^^^ 

and  the   "veins"  ^       ^ 

,.     ,         .         Fig.  nq.—  Egg  and  Molts  of  a  Grasshopper. 
in   it  studied.     A 

thin  bit  of  an  abdominal   segment  containing   a  spiracle 
will  show  the  structure  of  these  important  organs. 

Growth  of  the  Grasshopper.  — Some  species  hibernate  in 
sheltered  places  and  lay  eggs  in  the  spring,  but  adult  species 
are  scarce  at  that  season.  Most  species  lay  the  eggs  in  the 
fall;  these  withstand  the  cold  and  hatch  out  in  the  spring. 
Those  hatched  from  one  set  of  eggs  sometimes  stay  together 
for  a  few  days.  They  eat  voraciously,  and  as  they  grow,  the 
soft  skin  becomes  hardened  by  the  deposit  of  horny  sub- 
stance called  chitin.  This  prevents  further  growth  until  the 
insect  molts,  the  skin  first  splitting  above  the  prothorax.  After 
hatching,  there  are  five  successive  periods  of  growth.  At 
which  molt  do  the  very  short  wings  first  appear  ?   (Fig.  1 15.) 


yo 


A.XIMAL   BIOLOGY 


After  the  last  molt  the  animal  is  complete,  and  changes 
no  more  in  size  for  the  rest  of  its  life.  There  has  been  an 
attempt  among  writers  to  restrict  the  term 
grasshopper  to  the  long  winged,  slender 
species,  and  to  call  the  shorter  winged, 
stouter  species  locusts  according  to  old 
English  usage. 

|  Economic  Importance  of  Grasshoppers.  — 
Great  injury  is  often  done  to  vegetation  by 
grasshoppers  ;  however,  the  millions  of  tiny 
but  ravenous  eaters  hatched  in  early  spring 
are  usually  soon  thinned  out  by  the  birds.  The  migra- 
tory locusts  constitute  a  plague  when  they  appear,  and 


Fig.  116. — 

C<  ii_'K  ROACH. 


Fig.  117. 


Praying  Mantis,  or  devil's 
horse. 


Fig.  118.  —  Cricket. 


they  have  done  so  since  ancient  times.  The  Rocky  Moun- 
tain locusts  flying  eastward  have  darkened  the  sky,  and 
where  they  settled  to  the  earth 
ate  almost  every  green  thing. 
In  1874-5  they  produced  almost 
a  famine  in  Kansas,  Nebraska,  FlG-  ™9-  — mole  cricket. 
and  other  Western  states.  The  young  hatched  away 
from  the  mountains  were  not  healthy, 
and  died  prematurely,  and  their  devas- 
tations came  to  an  end.  Of  course  the 
migrations  may  occur  again.  Packard 
calculates  that  the  farmers  of  the 
Leg°of  Mole  West  lost  $200,000,000  because  of  their 
Cricket,    x  3.  ravages  in  1874-5. 


INSECTS 


71 


The  cockroaches  (Fig.  116),  kindred  of  the  grasshoppers, 
are  household  pests  that  have  migrated  almost  everywhere 
that  ships  go.  The  praying  mantis  (Fig.  117),  or  devil's 
horse,  also  belongs  to  this  order.  It  is  beneficial,  since  it 
destroys  other  insects.  Which  of  its  legs  are  specialized  ? 
The  walking  stick  (Fig.  121)  and  cricket  (Fig.  118),  like 
most  members  of  the  order,  are  vegetarian. 

Are  grasshoppers  more  common  in  fields  and  meadows, 
or  in  wooded  places  ?  How  many  different  colors  have  you 
seen  on  grasshoppers  ?  Which 
colors  are  most  common  ? 

Grasshoppers  are  very  scarce 
in  Europe  as  they  love  dry, 
warm  countries.  Why  do  lo- 
custs migrate  ?  Give  an  in- 
stance in  ancient  times. 

How  long  do  most  grass- 
hoppers live  ?  Does  a  grass- 
hopper spread  its  wings  before 
it  flies  ?  Does  it  jump  and  fly 
together  ?  Can  it  select  the 
place  for  alighting  ? 


Note   to  Teacher.  —  Field  work  in 

r,  ,  u  1  1  u  *  *■  -c  <.„,*.■;*.  Fig.  121.  — Four  Walking  Stick 
Zoology  should  be  systematic.    Every  trip      x  1U- 

1  1  r  ■  •  3  j  il  -l.   i-        c  Insects. 

has  a  definite  region  and  definite  line  01 

study  in  view,  but  every  animal  seen  should  be  noted.  The  habitat,  adapta- 
tion by  structure  and  habits  to  the  environment,  relations  to  other  animals, 
classification  of  animals  seen,  should  be  some  of  the  ideas  guiding  the  study. 
The  excursions  may  be  divided  somewhat  as  follows,  according  as  opportunities 
offer:  Upland  woods, lowland  woods,  upland  pastures,  fields,  swamps,  a  fresh- 
water lake,  a  pond,  lower  sea  beach,  higher  sea  beach,  sand  hills  along  shore, 
roadside,  garden,  haunts  of  birds,  insect  visits  to  flowers,  ground  insects, 
insects  in  logs. 

An  alphabetical  letter  file  may  be  used  for  filing  individual  field  observations. 
These  should  be  placed  before  the  class  orally  or  in  writing.  If  accepted  as 
reliable  (repeated  and  revised  if  necessary),  the  observations  should  be  filed 


J  2  ANIMAL   BIOLOGY 

away  and  credit  given  the  student  on  a  regular  scale.  Thus  will  grading  and 
marks  he  placed  to  encourage  intelligent  study  of  nature  rather  than  book 
or  laboratory  cram.  One  percent  to  be  added  to  the  final  grade  may  be  cred- 
ited for  every  species  of  pupa,  every  rare  insect  (with  an  observed  fact  as  to  its 
habits)  brought  in,  every  bird  migration  observed,  every  instance  of  protective 
coloration,  mimicry  (p.  146),  outwitting  of  enemy,  instance  of  injurious  insects, 
and  how  to  combat  them,  etc.  Sharp  eyes  and  clear  reasoning  will  then  count 
as  much  on  school  grades  as  a  memory  for  words  or  mechanical  following  of 
laboratory  directions.  On  scale  of  100,  class  work  =  50,  examination  =  25, 
field  work  =  25. 

Collecting  Insects.  —  In  cities  and  towns  insects,  varying  with 
the  season,  are  attracted  by  electric  lights.  Beetles  and  bugs  will 
be  found  under  the  lights,  moths  on  posts  near  the  lights,  grass- 
hoppers and  crickets  and  other  insects  in  the  grass  near  by.  A 
lamp  placed  by  a  window  brings  many  specimens.  In  the  woods 
and  in  rocky  places  insects  are  found  under  logs  and  stones,  and 
under  the  bark  of  dead  trees.  In  open  places,  prairies,  meadows, 
and  old  fields  with  grass  and  flowers,  it  will  be  easy  to  find  grass- 
hoppers, butterflies,  and  some  beetles.  Ponds  and  streams  are 
usually  rich  in  animal  forms,  such  as  bugs  and  beetles,  which  swim 
on  or  under  the  surface,  and  larvae  of  dragon  flies  crawling  on  the 
bottom.  Dragon  flies  and  other  insects  that  lay  eggs  on  the  water 
are  found  flying  in  the  air  above.  (In  the  spring,  newly  hatched 
crawfish,  tadpoles,  and  the  eggs  of  frogs  and  toads  should  also  be 
collected,  if  found.)  Moths  may  be  caught  at  night  by  daubing 
molasses  or  sirup  made  from  brown  sugar  upon  the  trunks  of 
several  trees,  and  visiting  the  trees  at  intervals  with  a  lantern. 

An  insect  net  for  catching  butterflies  and  for  dredging  ponds 
may  be  made  by  bending  a  stout  wire  into  a  circle  one  foot  in 
diameter,  leaving  enough  straight  wire  to  fasten  with  staples  on  an 
old  broomstick.  To  the  frame  is  fastened  a  flour  sack,  or  cone 
made  of  a  piece  of  mosquito  netting. 

Butterflies  and  moths  should  be  promptly  killed,  or  they  will 
beat  their  wings  to  pieces.  The  quickest  method  is  by  dropping 
several  drops  of  gasoline  upon  the  ventral  (under)  side  of  the 
thorax  and  abdomen.  (Caution  :  Gasoline  should  never  be  used 
near  an  open  fire,  or  lamp,  as  explosions  and  deaths  result  from 
the  flame  being  led  through  the  gasoline-saturated  air  to  the  vessel 
containing  it.) 


INSECTS 


73 


A  cigar  box  and  a  bottle  with  a  notched  cork  may  be  used  for 
holding  specimens.  Cigar  boxes  may  be  used  for  holding  collec- 
tions of  dried  insects.  Cork  or  ribbed  packing  paper  may  be 
fixed  in  the  bottom  for  supporting  the  insect  pins.  Moth  balls  or 
tobacco  may  be  placed  in  each  box  to  keep  out  the  insect  pests 
which  infest  collections. 

It  is  pleasant  and  profitable  to  take  to  the  fields  a  small  book 
like  this  one,  or  even  Comstock's  "  Manual  of  Insects,"  or  Kel- 
logg's  "  American  Insects,"  and  study  the  insects  and  their  habits 
where  they  are  found. 

Captured  insects  which,  in  either  the  larval  or  perfect  stage,  are 
injurious  to  vegetation,  should  always  be  killed  after  studying  their 
actions  and  external  features,  even  if  the  internal  structure  is  not  to  be 
studied.  Beneficial  insects,  such  as  ladybugs,  ichneumon  flies,  bees, 
mantis  (devil's  horse),  dragon  flies,  etc.,  should  be  set  free  uninjured. 

Anatomy  and  General  Characteristics  of  the  Class 

Insecta 

The  body  of  an  insect  (e.g.  a  wasp,  Fig.  122)  is  divided 
by  means  of  two  marked  narrowings  into  three  parts : 
the  head  (A'),  chest  (B),  and 
abdomen  {H). 

The  head  is  a  freely  movable 
capsule  bearing  four  pairs  of 
appendages.  Hence  it  is  re- 
garded as  having  been  formed 
by  the  union  of  four  rings, 
since  the  ancestor  of  the  insects 
is  believed  to  have  consisted 
of  similar  rings,  each  ring 
bearing  a  pair  of  unspecialized 
legs.  The  early  grub  or  caterpillar  stage  of  insects  is 
believed  to  resemble  somewhat  the  ancestral  form. 

The  typical  mouth  parts  of  an  insect  (Fig.  123),  named 
in  order  from  above,  are  (1)  an  upper  lip  (labrum,  ol),  (2)  a 


Fig.  122. — A  Wasp. 


74  ANIMAL   BIOLOGY 

pair  of  biting  jaws  (mandibles,  ok),  (3)  a  pair  of  grasp- 
ing  jaws  (maxillae,  A,  B),  and  (4)  a  lower  lip  (labium,  m,a,  b). 
The  grasping  jaws  bear  two  pairs  of 
"'  <?\"*  jointed  jaw  fingers  (maxillary  palpi, 

D,  C),  and  the  lower  lip  bears  a  pair 
$%&/         °f  similar  1JP  nnScrs  (labial  palpi,  d). 
f    i  r^L|\  ^he  biting  jaws  move  sideways  ;  they 

vV''--v*-^l!k  usually  have  several  pointed  notches 
which  serve  as  teeth.  Why  should  the 
grasping  jaws  be  beneath  the  chewing 

fig.  123.-  MoriH         jaws  ?     why  is  it  better  for  the  lower 
Parts  of  Beetle.  . . 

lip  to  have  fingers  than  the  upper  lip  ? 

Why  are   the   fingers  (or  palpi) 

jointed  ?     (Watch  a  grasshopper 

or  beetle  eating.)    Why  does  an 

insect  need  grasping  jaws  ? 

The  chest,  or  thorax,  consists 

of  three  rings  (Fig.  124)  called 

the     front     thorax     (prothorax), 

middle  thorax  (mesothorax)  and 

hind     thorax     (metathorax),     or 

first,     second,    and    third    rings.  W 

The      first      ring       Fig.  124.  —  External  Parts 

Jib.      /  u  4.1         c  of  a  Beetle. 

fj  bears     the     first 

pair    of    legs,   the   second    ring   bears   the 

second  pair  of  legs  and  the  upper  or  front 

wings,  and  the  third  ring  bears  the  third 

pair  of  legs  and  the  under  or  hind  wings. 

The  six  feet  of  insects  are  characteristic 

Fig.  125.  — leg       0f  them,  since  no  other  animals  have  that 
of  Insect. 

number,  the  spider  having  eight,  the  craw- 
fish and  crabs  having  ten,  the  centipedes  still  more,  while 
the  birds  and  beasts  have  less  than  six.     Hence  the  insects 


INSECTS  75 

are  sometimes  called  the  Six-Footed  class  {Hcxapoda). 
The  insects  are  the  only  animals  that  have  the  body  in 
three  divisions.  Man,  beasts,  and  birds  have  only  two 
divisions  (head  and  trunk) ;   worms  are  not  divided. 

Define  the  class  insecta  by  the  two  facts  characteristic  of 
them  {i.e.  possessed  by  them  alone),  viz.  :  Insects  are  ani- 
mals with  and .  Why  would  it  be  ambig- 
uous to  include  "  hard  outer  skeleton  "  in  this  definition  ?  To 
include  "bilateral  symmetry"?  "Segmented  body  "?  The 
definition  of  a  class  must  include  all  the  individuals  of  the  class, 
and  exclude  all  the  animals  that  do  not  belong  to  the  class. 

The  leg  of  an  insect  (Fig.  125)  has  five  joints  (two  short 
joints,  two  long,  and  the  foot).  Named  in  order  from  above,  they 
are  (1)  the  hip  (coxa),  (2)  thigh  ring  (trochanter),  (3)  thigh 
(femur),  (4)  the  shin  (tibia),  (5)  the  foot,  which 
has  five  parts.  Which  of  the  five  joints  of  a 
wasp's  leg  (Fig.  122)  is  thickest?  Slenderest? 
Shortest?  One  joint  (which?)  of  the  foot 
(Fig.  122)  is  about  as  long  as  the  other  four  FlG_  I26. _  fooT'of 
joints  of  the. foot  combined.  Is  the  relative  fly,  with  climbing 
length  of  the  joints  of  the  leg  the  same  in  Pads- 
grasshoppers,  beetles,  etc.,  as  in  the  wasp  (Figs.)?  Figure  125  is 
a  diagram  of  an  insect's  leg  cut  lengthwise.  The  leg  consists  of 
thick-walled  tubes  {0,  n)  with  their  ends  held  together  by  thin, 
easy-wrinkling  membranes  which  serve  as  joints.  Thus  motion  is 
provided  for  at  the  expense  of  strength.  When  handling  live 
insects  they  should  never  be  held  by  the  legs,  as  the  legs  come 
off  very  easily.  Does  the  joint  motion  of  insects  most  resemble 
the  motion  of  hinge  joints  or  ball-and-socket  joints?  Answer  by 
tests  of  living  insects.  There  are  no  muscles  in  th'e  foot  of  an 
insect.  The  claw  is  moved  by  a  muscle  {m)  in  the  thigh  with  which 
it  is  connected  by  the  long  tendon  (z,  s,  t,  v).  In  which  part  are 
the  breathing  muscles?  As  the  wings  are  developed  from  folds 
of  the  dorsal  skin,  the  wing  has  two  layers,  an  upper  and  a  lower 
layer.  These  inclose  the  so-called  "  nerves  "  or  ribs  of  the  wing, 
each  of  which  consists  of  a  blood  tube  inclosed  in  an  air  tube. 


76 


ANIMAL    BIOL OGY 


The  abdomen  in  various  species  consists  of  from  five 
to  eleven  overlapping  rings  with  their  foldlike  joints  be- 
tween them.  Does  each  ring  overlap  the  ring  in  front 
or  the  one  behind  it  ? 

The  food  tube  (Fig.  127)  begins  at  the  mouth,  which 
usually  contains  salivary  glands  (4,  Fig.  127).  What 
is  the  color  of  the  grasshopper's  saliva  ?  The  food  tube 
expands  first  into  a  croplike  enlargement ;  next  to  this 
is  the  stomach  (6,  Fig.  127),  which  resembles  the  gizzard 
,?  %\ 

Ita     Ma 


Fig.  127.  —  Viscera  of 
Grasshopper.  Key 
in  text.  Compare  with 
Fig.  114. 


Fig.  128.  —  Air  Tubes  of  Insect. 


in  birds,  as  its  inner  wall  is  furnished  with  chitinous  teeth 
(b,  Fig.  114).  These  reduce  the  food  fragments  that  were 
imperfectly  broken  up  by  the  biting  jaws  before  swallow- 
ing. Glands  comparable  to  the  liver  of  higher  animals 
open  into  the  food  tube  where  the  stomach  joins  the  small 
intestine.  At  the  junction  of  the  small  and  large  intestine 
(9)  are  a  number  of  fine  tubes  (8)  which  correspond  to 
kidneys  and  empty  their  secretion  into  the  large  intestine. 
The  breathing  organs  of  the  insects  are  peculiar  to 
them   (see  Fig.    128).     They    consist   of  tubes  which  are 


INSECTS 


77 


i 


t      V 


kept  open  by  having  in  their  walls  continuous  spirals  of 
horny  material  called  cJiitin.  Most  noticeable  are  the 
two  large  membranous  tubes  filled  with  air  and 
situated  on  each  side  of  the  body.  Do  these 
tubes  extend  through  the  thorax?  (Fig.  128.)  The 
air  reaches  these  two  main  tubes  by  a  number 
of  pairs  of  short  windpipes,  or  trachcas,  which 
begin  at  openings  {spiracles).  In  which  division 
are  the  spiracles  most  numerous?     (Fig.  128.) 

Which  division  is 
v..v4.J^_  .y^iW   _/tJV  V^4K  without  spiracles  ? 

"ir'5<K  }lK  3  W  £    Could  an  insect 

5CtHK  JM  5       [      be    drowned,    i.e. 


pq 

s.  W^; 
h* 

Fig.  129. 
Insect's 

H  EA  RT 

(plan). 


Fig.  130.  — Diagrams  of  Evolution 
of  Pericardial  Sac  around  in- 
sect's heart  from  a  number  of  veins 
(Lankester). 


smothered,  by  holding  its 
body  under  water  ?  Could 
it  be  drowned  by  immersing 
all  of  it  but  its  head  ?  The 
motion  of  the  air  through 
the  breathing  tubes  is  caused  by  a  bellowslike  motion  of  the 
abdomen.  This  is  readily  observed  in  grasshoppers,  beetles, 
and  wasps.  As  each  ring  slips  into  the  ring  in  front  of  it, 
the  abdomen  is  shortened,  and  the  impure  air,  laden  with 
carbon  dioxid,  is  forced  out.  As  the  rings  slip  out,  the 
abdomen  is  extended 
and  the  fresh  air  comes 
in,  bringing  oxygen. 

The  Circulation.  — 
Near  the  dorsal  surface 
of  the  abdomen  (Fig. 
131)  extends  the  long,  slender  heart  (Fig.  129).  The  heart 
has  divisions  separated  by  valvelike  partitions.  The  blood 
comes  into  each  of  the  heart  compartments  through  a  pair 
of  openings.     The  heart  contracts  from  the  rear  toward 


-y  iq 


Fig.  131.  —  Position  of  Insect's  Heart, 
food  tube,  and  nerve  chain. 


7* 


ANIMAL  BIOLOGY 


the  front,  driving  the  blood  forward.  The  blood  contains 
bodies  corresponding  to  the  white  corpuscles  of  human  blood, 
but  lacks  the  red  corpuscles  and  the  red  color.  The  blood 
is  sent  even  to  the  wings.  The  ribs  on  the  wings  consist  of 
blood  tubes  inclosed  in  air  tubes,  so  that  the  blood  vessels 
are  surrounded  by  air,  and  the  purification  of  the  blood  is 

taking  place  throughout  the  course 
of  the  circulation.  Hence  the  im- 
perfect circulation  is  no  disadvan- 
tage. The  perfect  provision  for 
supplying  oxygen  explains  the 
remarkable  activity  of  which  in- 
sects are  capable  and  their  great 
strength,  which,  considering  their 
size,  is  unequaled  by  any  other 
animals. 

The  Nervous  System.  —  The 
heart  in  backboned  animals,  e.g. 
man,  is  ventral  and  the  chief  nerve  trunk  is  dorsal.  As 
already  stated,  the  heart  of  an  insect  is  dorsal ;  its  chief 
nerve  chain,  consisting  of  a  double  row  of  ganglia,  is  near 
the  ventral  surface  (Fig.  131).  All  the  ganglia  are  below 
the  food  tube  except  the  first  pair  in  the  head,  which  are 
above  the  gullet.  This  pair  may  be  said  to 
correspond  somewhat  to  the  brain  of  backboned 
animals ;  the  nerves  from  the  eyes  and  feelers 
lead  to  it.  With  social  insects,  as  bees  and 
ants,  it  is  large  and  complex  (Fig.  132).  In  a 
typical  insect  they  are  the  largest  ganglia. 

The  Senses.  — ■  The  sense  of  smell  of  most  in- 
sects is  believed  to  be  located  in  the  feelers. 
The  organ  of  hearing  is  variously  located  in  different  in- 
sects.    Where  is  it  in  the  grasshopper  ?     The  organs  of 


Fig.  132.  —  Nervous  Sys- 
1  em  of  Bee. 


INSECTS 


79 


Fl(J.  134.  — Diagram 
of  simple  eye  of 
insect. 

L,  lens;  iV,  optic 
nerve. 


^SSs 


W 


sight  are  highly  developed,  and  consist  of  two  compound 
eyes  on  the  side  of  the  head  and  three  simple  eyes  on  the 
top  or  front  of  the  head  between  the  com- 
pound eyes.     The  simple  eye  has  nerve 
cells,   pigments,   and    a   lens    resembling 
the  lens  in  the  eyes  of  vertebrates  (Fig. 
134).     The  compound  eye  (Fig.  135)  has 
thousands   of   facets,   usually   hexagonal, 
on  its  surface,  the  facets  being  the  outer 
ends   of   cones   which    have   their  inner 
ends  directed  toward  the  center  of  the 
eye.     It  is    probable   that  the   large,   or 
compound,  eyes  of  insects  only  serve  to  distinguish  bright 
objects  from   dark  objects.     The  simple  eyes  afford  dis- 
tinct images  of  objects  within  a 
few  inches  of  the  eye.     In  gen- 
eral, the  sight  of  insects,  contrary 
to  what  its  complex  sight  organs 
would  lead  us  to  expect,  is  not  at 
all  keen.     Yet  an  insect  can  fly 
through  a  forest  without  striking 
a  twig  or  branch.    Is  it  better  for 
the  eyes  that  are  immovable  in 
the   head  to   be  large  or  small  ? 
Which  has  comparatively  larger 
eyes,  an  insect  or  a  beast  ? 
Inherited   Habit,  or  Instinct.  —  Insects    and   other  ani- 
mals inherit  from  their  parents  their  particular  form  of 
body  and  of  organs  which  perform  the  different  functions. 
For  example,  they  inherit  a  nervous  system  with  a  struc- 
ture similar  to  that  of  their  parents,  and  hence  with  a  ten- 
dency to  repeat  similar  impulses  and  acts.      Repeated  acts 
constitute  a  habit,  and  an  inherited  habit  is  called  an  in- 


Fig.  135. —Compound  Eye 
of  Insect. 

I,  hexagonal  facets  of  crystalline 
cones.    6,  blood  vessel  in  optic  nerve. 


80  ANIMAL  BIOLOGY 

stinct.  Moths,  for  example,  are  used  to  finding  nectar  in 
the  night-blooming  flowers,  most  of  which  are  white.  The 
habit  of  going  to  white  flowers  is  transmitted  in  the  struc- 
ture of  the  nervous  system  ;  so  we  say  that  moths  have 
an  instinct  to  go  to  white  objects ;  it  is  sometimes  more 
obscurely  expressed  by  saying  they  are  attracted  or  drawn 
thereby. 

Instincts  are  not  Infallible.  —  They  are  trustworthy  in 
only  one  narrow  set  of  conditions.  Now  that  man  makes 
many  fires  and  lights  at  night,  the  instinct  just  mentioned 
often  causes  the  death  of  the  moth.  The  instinct  to 
provide  for  offspring  is  necessary  to  the  perpetuation  of 
all  but  the  simplest  animals.  The  dirt  dauber,  or  mud 
wasp,  because  of  inherited  habit,  or  instinct,  makes  the 
cell  of  the  right  size,  lays  the  egg,  and  provides  food  for 
offspring  that  the  mother  will  never  see.  It  seals  stung 
and  semiparalyzed  spiders  in  the  cell  with  the  egg.  If 
you  try  the  experiment  of  removing  the  food  before  the 
cell  is  closed,  the  insect  will  bring  more  spiders ;  if  they 
are  removed  again,  a  third  supply  will  be  brought;  but  if 
taken  out  the  third  time,  the  mud  wasp  will  usually  close 
the  cell  without  food,  and  when  the  egg  hatches  the  grub 
will  starve. 

The  Development  of  Insects.  —  The  growth  and  molting 
of  the  grasshopper  from  egg  to  adult  has  been  studied. 
All  insects  do  not  develop  exactly  by  this  plan.  Some 
hatch  from  the  egg  in  a  condition  markedly  different  from 
the  adult.  The  butterfly's  egg  produces  a  wormlike  cater- 
pillar which  has  no  resemblance  to  the  butterfly.  After 
it  grows  it  forms  an  inclosing  case  in  which  it  spends  a 
quiet  period  of  development  and  comes  out  a  butterfly. 
This  change  from  caterpillar  to  butterfly  is  called  the 
metamorphosis.     The  life  of  an  insect  is  divided  into  four 


INSECTS 


81 


FlG.  136.  —  Measuring  worm, 
the  larva  of  a  moth. 


stages  :  (1)  egg,  (2)  larva,  (3)  pupa,  and  (4)  imago,  or  per- 
fect insect  (Figs.  136,  137,  138). 

The  e°"g  stage  is  one  of  development,  no  nourishment 
being  absorbed.  The  larval  stage  is  one  of  voracious  feed- 
ing and  rapid  growth.  In  the  pupa 
stage  no  food  is  taken  and  there  is 
no  growth  in  size,  but  rapid  devel- 
opment takes  place.  In  the  per- 
fect stage  food  is  eaten,  but  no 
growth  in  size  takes  place.  In  this 
stage  the  eggs  are  produced.  When 

f  there  is  very  little  resemblance  between  the 

larva  and  imago,  and  the  pupa  is  quiescent, 
the  metamorphosis,  or  change,  is  said  to  be 
complete.  When,  as  with  the  grasshopper, 
no  very  marked  change  takes  place  between 
the  larva  and  imago  (that  is  to  say,  during 
the  pupa  stage,  which  is  active),  the  meta- 
morphosis is  said  to  be  incomplete.  By 
studying  the  illustrations  and  specimens,  and  by  thinking 
of  your  past  observations  of  insects,  determine  which  of  the 
insects  in  the  following  list  have  a  complete  metamorpho- 
sis :  beetle,  house  fly,  grasshopper,  butterfly,  cricket,  wasp. 


Fig.  137.  —  Pupa 
of  a  mosquito. 


Fig.  138.  —  The  Four  Stages  of  a  Botfly,  all  enlarged. 

a,  egg  on  hair  of  horse  (bitten  off  and  swallowed) :  b,  larva;  c,  larva  with  hooks  for  holding 
to  lining  of  stomach;  d,  pupal  stage,  passed  in  the  earth;  e,  adult  horse  fly. 

G 


A  XI MA  I.    BIOLOGY 


TABLE  FOR  CLASSIFYING   INSECTS  (class  Insect  a)  INTO 
ORDERS 


A,  Biting   Insects ;    mouth    parts  for  grasping 
and  biting 

B,  Wingless;      changes      (metamorphosis) 

incomplete 
B.,  Under  wings  thinner  than  upper  wings, 
and  fold  like  a  fan  beneath  them  ;  changes 
incomplete 
B3  Upper  wings  hard  and  thick,  protecting 
under  wings,  which  fold  both  lengthwise 
and    crosswise    beneath    them ;    changes 
incomplete 
B4  All  four  wings  nearly  alike,  finely  veined, 
transparent 

Cj  Hind  wings  smaller  than  fore,  two 
or  three  filaments  attached  to  abdo- 
men, antennae  long ;  changes  com- 
plete 
C,  Hind  wings  not  smaller  than  fore; 
no  filaments  on  abdomen,  antennae 
inconspicuous ;  changes  incomplete 


Order 


No  Wings 

(Apterd) 
Fan  Wings 

(Or  t hop  t era) 

Sheath  Wings 

(  Coleopterd) 


Nerve  Wings 

(Xetiropterd) 


False  Nerve 
Wings 

(Pseudoneuropterd) 


A0  Sucking  Insects ;  mouth  parts  for  sucking 
or  licking 

Bx  Basal  half  of  upper  wing  usually  leathery, 
other  half  of  wing  transparent ;  lower  lips 
transformed  into  a  tube ;  true  bugs 

B2  Four  wings  covered  by  scales,  holding- 
jaws  (maxillae)  elongated  to  form  a  suck- 
ing tube  coiled  under  head ;  changes 
complete 

B;1  Four  wings,  membranous,  hind  wings 
hook  to  fore  wings  in  flight :  mouth  parts 
for  both  biting  and  sucking ;  abdomen 
with  sting ;  changes  complete 

B4  Two  wings,  mandibles  rudimentary, 
mouth  a  soft  beak 

B5  No  wings,  mandibles  rudimentary,  mouth 
a  horny  beak 


Half  Wings 

(Hemiptera) 

Scaly  Wings 

(Lepidopterd) 


Joined  Wings 

{Hymenopterd) 


Two  Wings 

(Dipterd) 

Lost  Wings 

(Sipkotwptera) 


INSECTS 


83 


Fig.  139.  — May  Fly.    What  order  (see  table)? 


Exercise  in  the  Use  of*the  Table  or  Key  — 

Write  the  name  of  the  order  after  each  of  the  fol- 
lowing names  of  insects  :  — 


Wasp  (Fig.  122) 
Weevil  (Fig.  163) 
Squash  bug  (  Fig.  184) 
Ant  lion  (Fig.  170) 
Dragon  fly  (Fig.  177) 
Ichneumon  fly  (Fig.  159) 


House  fly  (Fig.  172) 
Flea  (Fig.  173) 
Silver  scale  or  earwig 

(Fig.  140) 
Codling  moth  (Fig.  141) 
Botfly  (Fig.  138) 


Fig.  140. —  Silver 
Scale.   (Order?) 


Moths  and  Butterflies.  —  Order. 


?    Why (p.  82)? 

The  presence  of  scales  on  the  wings  is  a  never-failing 
test  of  a  moth  or  butterfly.  The  wings  do  not  fold  at  all. 
They  are  so  large  and  the  legs  so  weak  and  delicate 
that  the  butterfly  keeps  its  balance  with  difficulty  when 
walking. 

The  maxillae  are  developed  to  form  the  long  sucking 
proboscis.  How  do  they  fit  together  to  form  a  tube? 
(See  Fig.  147.)  The  proboscis  varies  from  a  fraction  of  an 
inch  in  the  "miller"  to  five  inches  in  some  tropical  moths, 
which  use  it  to  extract  nectar  from  long  tubular  flowers. 
When  not  in  use,  it  is  held  coiled  like  a  watch  spring  under 
the  head  (Fig.  148).  The  upper  lip  (labrum),  under  lip 
(labium),  and  lip  fingers  (labial  palpi)  are  very  small,  and 
the  mandibles  small  or  wanting  (Fig.  146). 

The  metamorphosis  is  complete,  the  contrast  between 
the  caterpillar  or  larva  of  the  moth  and  butterfly  and  the 
adult  form  being  very  great.  The  caterpillar  has  the 
three  pairs  of  jointed  legs  typical  of  insects;   these  are 


84  ANIMAL    BIOLOGY 

found  near  the  head  (Fig.  141).  It  has  also  from  three 
to  five  pairs  of  fleshy  unjointed  proplegs,  one  pair  of 
which  is  always  on  the  last  segment.  How  many  pairs 
of  proplegs  has  the  silkworm  caterpillar?  (Fig.  143.) 
The  measuring  worm,  or  looper  ?  (Fig.  136.)  The  pupa 
has  a  thin  shell.  Can  you  see  external  signs  of  the 
antennae,  wings,  and  legs  in  this  stage  ?  (Fig.  143.)  The 
pupa  is  concealed  by  protective  coloration,  and  is  some- 
times inclosed  in  a  silken  cocoon  which  was  spun  by  the 
caterpillar  before  the  last  molt.  Hairy  caterpillars  usually 
produce  butterflies,  and  the  naked  ones  usually  produce 
moths.  Hairy  ones  are  uncomfortable  for  birds  to  eat. 
The  naked  and  brightly  marked  ones  (warning  coloration) 
often  contain  an  acrid  and  distasteful  fluid.  The  injuries 
from  lepidoptera  are  done  in  the  caterpillar  stage.  The 
codling  moth  (Fig.  141)  destroys  apples  to  the  value  of 
$6,000,000  annually.  The  clothes  moth  (Fig.  171)  is  a 
household  pest.  The  tent  caterpillar  denudes  trees  of  their 
leaves.  The  only  useful  caterpillar  is  the  silkworm  (Fig. 
143).  In  Italy  and  Japan  many  of  the  country  dwellings 
have  silk  rooms  where  thousands  of  these  caterpillars  are 
fed  and  tended  by  women  and  children.  Why  is  the  cab- 
bage butterfly  so  called  ?  Why  can  it  not  eat  cabbage  ? 
Why  does  sealing  clothes  in  a  paper  bag  prevent  the 
ravages  of  the  clothes  moth  ? 

Flight  of  Lepidoptera.  —  Which  appears  to  use  more  ex- 
ertion to  keep  afloat,  a  bird  or  a  butterfly  ?  Explain  why. 
Of  all  flying  insects  which  would  more  probably  be  found 
highest  up  mountains  ?  How  does  the  butterfly  suddenly 
change  direction  of  flight  ?  Does  it  usually  fly  in  a  straight 
or  zigzag  course  ?  Advantage  of  this  ?  Why  is  zigzag 
flight  unnecessary  to  moths  ?  Bright  colors  are  protective, 
as    lepidoptera  are  in   greatest  danger  when   at   rest  on 


INSECTS 


flowers.  Are  the  brightest  colors  on  upper  or  under 
side  of  wings  of  butterfly  ?  Why  ?  (Think  of  the  colors 
in  a  flower.)  Why  is  it  better  for  moths  to  hold  their 
wings  flat  out  when  at  rest  ?  Where  are  moths  during 
the  day?  How  can  you  test  whether  the  color  of  the 
wings  is  %iven  by  the  scales  ? 

State  how  moths  and  butterflies  differ  in  respect  to  : 
body,  wings,  feelers,  habits  ;  abundance  of  scales. 

Insects  and  Flowers.  —  WTe  are  indebted  to  insects  for 
the  bright  colors  and  sweet  honey  of  flowers.  Flowers 
need  insects  to  carry  their  pollen  to  other  flowers,  as  cross- 
fertilization  produces  the  best  seeds.  The  insects  need  the 
nectar  of  the  flowers  for  food,  and  the  bright  colors  and 
sweet  odors  are  the  advertisements  of  the  flowers  to  at- 
tract insects.  There  were  no  flowers  in  the  world  before 
flying  insects  were  developed.  Moths,  butterflies,  and 
bees  carry  most  pollen  (see  Plant  Biology,  Chap.  VI). 

Comparative  Study.  —  Make  a  table  like  this,  occupying  entire  page 
of  notebook,  leaving  no  margins,  and  fill  in  accurately  :  — 


Grass- 
hopper 

Bctter- 

FLY 

Fly 
pp.  92,  93 

Dragon 
Fly,  p.  93 

Beetle 
pp.  90,  91 

Bee 
pp.  88,  89 

Number  and  kind 
of  wings 

Description  of  legs 

Antennae   (length, 
shape,  joints) 

Biting  or  sucking 
mouth  parts 

Complete  or  incom- 
plete metamor- 
phosis 

S6 


Illustrated  Studies 


■"-— ** 


Fig.  142. —  Cabbage  Buttekfly,  male 
and  female,  larva  and  pupa. 


Fig.  141.  — Codling  Moth,  from  egg  to 
adult.    (See  Farmers'  Bulletin,  p.  95.) 


Fig.  143. —  Life  History  of  Silkworm. 


Fig.  144.  —  Scales  from 
Butterflies'  Wings,  as 
seen  under  microscope. 


Illustrated  Studies 


87 


TO  THE  TEACHER:  These  illustrated  studies  require 
slower  and  more  careful  study  than  the  text.  One,  or  at 
most  frvo,  studies  will  suffice  for  a  lesson.  The  questions  can 
be  answered  by  studying  the  figures.  Weak  observers  will 
often  fail  and  they  should  not  be  told,  but  should  try  again 
until  they  succeed. 


Figs.  141-148.  Illustrated  Study  of  Lepidoptera.— 
Study  the  stages  in  the  development  of  codling  moth,  silk- 
worm moth,  and  cabbage  butterfly. 

Where  does  each  lay  its  eggs  ?  What  does  the  larva  of 
each  feed  upon  ?  Describe  the  pupa  of  each.  Describe 
the  adult  forms.  Find  the  spiracles  and  prolegs  on  the 
silkworm.  Compare  antenna  of  moth  and  butterfly. 
Which  has  larger  body  compared  to  size  of  wings  ? 

Describe  the  scales  from  a  butterfly's  wings  as  seen  under 
microscope  (144).  How  are  the  scales  arranged  on  moth's 
wing  (145)  ?  By  what  part  is  scale  attached  to  wing?  Do 
the  scales  overlap  ? 

Study  butterfly's  head  and  proboscis  (Figs.  146-148). 
What  shape  is  compound  eye  ?  Are  the  antennae  jointed  ? 
Is  the  proboscis  jointed  ?  Why  not  call  it  a  tongue  ? 
(See  text.) 

Which  mouth  parts  have  almost  disappeared  ?  What  is 
the  shape  of  cut  ends  of  halves  of  proboscis  ?  How  are 
the  halves  joined  to  form  a  tube  ? 

If  you  saw  a  butteifly  on  a  flower,  for  what  purpose 
would  you  think  it  was  there?  What,  if  you  saw  it  on  a 
leaf?  How  many  spots  on  fore  wing  of  female  cabbage 
butterfly?  (Fig.  124,  above.) 

Does  the  silkworm  chrysalis  fill  its  cocoon  ?  Eggs  may 
be  obtained  from  U.  S.  Dept.  of  Agriculture. 


Fig.  145.-81  vles 
on  Moth's  Wing. 


Fig.  146.  —  Head 
of  Butterfly. 


Fig.  148. —Head 
of   Butterfly 

(side  view). 


Fig.  147.  — Section 
of  Proboscis  of 
butterfly  showing 
lapping  joint  and 
dovetail  joint. 


88 


Illustrated  Studies 


Fig.  156. 


Fig.  157. 


Fig.  158.-- Anatomy  of  bee. 


Figs.  149-161.  Illustrated 
Study  of  Bees  and  their  Kin- 
dred. —  Head  of  worker  (Fig. 
149)  :  o,  upper  lip ;  ok,  chew- 
ing jaws  ;  uk,  grasping  jaws ; 
kt,  jaw  finger :  //,  lip  finger ; 
2,  tongue. 

How  do  heads  of  drone 
(150)  "and  queen  (151)  differ 
as   to   mouth,    size  of  the  two 

compound  eyes,  size  and  posilion  of  the  three  simple  eyes  ?  Is  the  head  of  a 
worker  more  like  head  of  drone  or  head  of  queen  ?  Judging  bv  the  head,  which 
is  the  queen,  drone,  and  worker  in  Figs.  154-156  ?  Which  of  the  three  is  largest? 
Smallest  ?     Broadest  ? 

Figure  152  shows  hind  leg  of  worker.  What  surrounds  the  hollow,  us,  which 
serves  as  pollen  basket  ?  The  point,  fh,  is  a  tool  for  removing  wax  which  is 
secreted  (c,  Fig.  157)  between  rings  on  abdomen.  In  Fig.  158,  find  relative 
positions  of  heart,  v,  food  tube,  and  nerve  chain.  Is  crop,  /,  in  thorax  or  abdo- 
men ?  In  this  nectar  is  changed  to  honey,  that  it  may  not  spoil.  Compare 
nerve  chain  in  Fig.  132. 


Illustrated  Studies 


89 


Compare  the  cells  of 
bumble  bee  (Fig.  153)  with 
those  of  hive  bee.  They 
differ  not  only  in  shape  but 
in  material,  being  made  of 
web  instead  of  wax,  and 
they  usually  contain  larvae 
instead  of  honey.  Only  a 
few  of  the  queens  among 
buml»le  bees  and  wasps 
survive  the  winter.  How 
do  ants  and  honey  bees 
provide  for  the  workers 
also  to  survive  the  win- 
ter ?  Name  all  the  social 
insects  that  you  can  think  of.  Do 
they  all    belong  to   the    same  order  ? 

The  ichneumon  fly  shown  enlarged  in 
Fig.  159  lays  its  eggs  under  a  caterpillar's 
skin.  What  becomes  of  the  eggs  ?  The 
true  size  of  the  insect  is  shown  by  the 
cross  lines  at  a.  The  eggs  are  almost 
microscopic  in  size.  The  pupae  shown 
(true  size)  on  caterpillar  are  sometimes 
mistaken  for  eggs.  The  same  mistake  is 
made  about  the  pupa  cases  of  ants. 
Ichneumon  flies  also  use  tree-borers  as 
"  hosts  "  for  their  eggs  and  larva.  Is 
this  insect  a  friend  of  man  ? 

The  digging  wasp  (Figs.  160  and  161) 
supplies   its   larva    with  caterpillars    and 
closes  the  hole,  sometimes  using  a  stone 
as  pounding  tool.   Among  the  few 
other  uses  of  tools  among    lower 
animals     are    the   elephant's    use 
of  a  branch  for  a   fly  brush,  and 
the  ape's  use  of  a  walking  stick. 
This    wasp    digs    with    fore   feet 
like   a   dog    and    kicks    the    dirt 
out    of   the    way    with    its    hind 
feet. 

Are  the  wings  of  bees  and 
wasps  more  closely  or  less 
closely  veined  than  the  wings 
of  dragon  flies?  (Fig.  177.) 
For  an  interesting  account 
of  the  order  "  Joined-wings" 
(bees  and  their  kindred)  see 
Comstock's  "  Ways  of  the  Six- 
footed,"  Ginn  &  Co. 


Fig.       ^\3*  ^> 

160.   .^vfx.  iS-^.kfc; 


Fig.  161.  —  Wasp  using  pebble. 

From  Peckham's  "  Solitary  Wasps," 

Houghton,  Mifflin  &  Co. 


90 


Illustrated  Studies 


Illustrated 
Study  of 
Beetles. 


FiG.  102.  —  Diving  beetle  (Dysticus),  with  larva,  a.  FiG.  163. — Weevil. 


Fig.   166.  — Click  beetle. 


Fig.  167.  — May  Beetle. 


Fig.  168. 


^^4A  iS^/i/k  Ui 


FIG.  169.  —  Colorado  beetle  (potato  bug). 


Illustrated  Studies 


91 


Illustrated  Study  of  Beetles  (Figs.  162-169). — Write  the  life  history  of  the 
Colorado  beetle,  or  potato  bug  (Fig.  169),  stating  where  the  eggs  are  laid  and  describ- 
ing the  form  and  activities  of  each  stage  (the  pupal  stage,  b,  is  passed  in  the  ground). 

Do  the  same  for  the  May  beetle  (Figs.  167-168).  (It  is  a  larva — the  white 
grub — for  three  years;  hogs  root  them  up.)  Beetles,  like  moths,  maybe  trapped 
with  a  lantern  set  above  a  tub  of  water. 

Where  does  a  Scarab  (or  sacred  beetle  of  the  Egyptians,  also  called  tumble 
bug  (Fig.  164),  lay  its  eggs  (Fig.  165)?     Why? 

How  does  the  click  beetle,  ox  jack  snapper  (Fig.  166) ,  threw  itself  into  the  air? 
For  what  puipose  ? 

The  large  proboscis  of  the  weevil  (Fig.  163)  is  used  for  piercing  a  hole  in  which 
an  egg  is  laid  in  grain  of  corn,  boll  of  cotton,  acorn,  chestnut,  plum,  etc. 

How  are  the  legs  and  body  of  the  diving  beetle  suited  for  swimming  (Fig.  162)  ? 
Describe  its  larva. 

What  is  the  shape  of  the  lady  bug  (Fig.  97)  ?  It  feeds  upon  plant  lice  (Fig.  185) . 
Is  any  beetle  of  benefit  to  man  ? 


Fig.  170.  —  Life  history  of  ant  lion. 

Illustrated  Study  of  Ant  Lion,  or  Doodle  Bug  (Fig.  170).— Find  the  pitfall 
(what  shape?) ;  the  larva  (describe  it)  ;  the  pupa  case  (ball  covered  with  web  and 
sand) ;  the  imago.     Compare  imago  with  diagon  fly  (Fig.   177). 

How  does  ant  lion  prevent  ant  from  climbing  out  of  pitfall  (see  Fig.  170)  ? 
What  is  on  edge  of  nearest  pitfall?     Explain. 

Ant  lions  may  be  kept  in  a  box  half  filled  with  sand  and  fed  on  ants.  How  is 
the  pitfall  dug?     What  part  of  ant  is  eaten  ?     How  is  unused  food  removed? 

How  long  is  it  in  the  larval  state  ?  Pupal  state  ?  Keep  net  over  box  to  pre- 
vent adult  from  flying  away  when  it  emerges. 


92 


Illustrated  Studies 


Fig.  171. 


%£&% 


FIG.  173.  —  Metamorphosis  of  flea. 


a 
FlG.    172.  —  Metamor- 
phosis of   house  fly 
(enlarged). 


Fig.  175.  —  Bed  bug.  x  5. 


Fig.  176.  —  Life  history  of  mosquito. 


Illustrated  Studies 


93 


Illustrated  Study  of  Insect  Pests  (Figs.  171-176).  — Why  does  the  clothes 
moth  (171)  lay  its  eggs  upon  woolen  clothing  ?  How  does  the  larva  conceal  itself  ? 
The  larva  can  cut  through  paper  and  cotton,  yet  sealing  clothes  in  bags  of  paper 
or  cotton  protects  them.     Explain. 

The  house  Jiy  eats  liquid  sweets.  It  lays  its  eggs  in  horse  dung.  Describe  its 
larval  and  pupal  forms.  Banishing  horses  from  city  would  have  what  beneficial 
effect  ? 

Describe  the  louse  and  its  eggs,  which  are  shown  attached  to  a  hair,  natural  size 
and  enlarged. 

Describe  the  bed  bug.  Benzine  poured  in  cracks  kills  bed  bugs.  Do  bed 
bugs  bite  or  suck  ?     Why  are  they  wingless  ? 

Describe  the  larva,  /,  pupa,  g,  and  the  adult  fiea,  all  shown  enlarged.  Its 
mandibles,  b,  b,  are  used  for  piercing.  To  kill  fleas  lather  dog  or  cat  completely 
and  let  lather  remain  on  five  minutes  before  washing.  Eggs  are  laid  and  first 
stages  passed  in  the  ground. 

How  does  the  mosquito  lay  its  eggs  in  the  water  without  drowning  (176)  ?  Why 
are  the  eggs  always  laid  in  still  water  ?  Which  part  of  the  larva  (wiggletail)  is  held 
to  the  surface  in  breathing  ?  What  part  of  the  pupa  (called  tumbler,  or  bull  head) 
is  held  to  the  surface  in  breathing?  Give  differences  in  larva  and  pupa.  Where 
does  pupa  change  to  perfect  insect  ?  Describe  mouth  parts  of  male  mosquito  (at 
left)  and  female  (at  right).  Only  female  mosquitoes  suck  blood.  Males  suck 
juice  of  plants.  Malarial  mosquito  alights  with  hind  end  of  body  raised  at  an 
angle.  For  figure  see  Human  Biology,  Chap.  X.  Why  does  killing  fish  and  frogs 
increase  mosquitoes?  1  oz.  of  kerosene  for  15  ft.  of  surface  of  water,  renewed 
monthly,  prevents  mosquitoes. 

What  is  the  use  to  the  squash  bug  (Fig.  184)  of  having  so  bad  an  odor  ? 


Fig.  177.  Illustrated  Study  of  Dragon  Fly.  —  3  shows  dragon  fly  laying  its 
eggs  in  water  while  poised  on  wing.  Describe  the  larval  form  (water  tiger).  The 
extensible  tongs  are  the  maxillae  enlarged.  The  pupa  (1)  is  active  and  lives  in 
water.  Where  does  transformation  to  adult  take  place  (5)  ?  Why  are  eyes  of 
adult  large  ?    its  legs  small  ?     Compare  front  and  hind  wings. 

Do  the  eyes  touch  each  other  ?  Why  is  a  long  abdomen  useful  in  flight  ? 
Why  would  long  feelers  be  useless?  What  is  the  time  of  greatest  danger  in  the 
development  of  the  dragon  fly  ?  What  other  appropriate  name  has  this  insect  ? 
Why  should  we  never  kill  a  dragon  fly  ? 


94 


Illustrated  Studies 


Fig.  183.  —  Foot  of  spider. 


Illustrated  Study  of  Spiders  (Figs.  178-183). —The  tarantula,  like  most  spi- 
ders, has  eight  simple  eyes  (none  compound).  Find  them  (Fig.  178).  How  do 
spiders  and  insects  differ  in  body  ?  Number  of  legs  ?  Which  have  more  joints  to 
legs?  Does  trap-door  spider  hold  the  door  closed  (Fig.  179)?  How  many  pairs 
of  spinnerets  for  spinning  web  has  a  spider  (S/>w,  180)  ?  Foot  of  spider  has  how 
many  claws  ?  How  many  combs  on  claws  for  holding  web  ?  Spiders  spin  a 
cocoon  for  holding  eggs.  From  what  part  of  abdomen  are  eggs  laid  (£,  182; 
2,  181)  ?  Find  spider's  air  sacs,  hi.  Fig.  181 ;  spinning  organs,  s/> ;  fang,  kf  \  poison 
gland,  g;  palpi,  kt\  eyes,  an  ;  nerve  ganglia,  og,  ug\  sucking  tube,  sr  ;  stomach,  d\ 
intestine,  ma\  liver,  le ;  heart,  k,  (black)  ;  vent,  a.  Give  two  reasons  why  a  spider 
is  not  an  insect.  How  does  it  place  its  feet  at  each  step  (Fig.  no)  ?  (Does  the 
size  of  its  nerve  ganglia  indicate  great  or  little  intelligence  ?  Why  do  you  think 
first  part  of  body  corresponds  to  both  head  and  thorax  of  insects  ? 


LVSECTS 


95 


Fig.  184.  —  Squash  bug,  or 
stink  bug;. 


The  following  Farmer's  Bulletins  are  available  for»free 
distribution  to  those  interested,  by  the  U.  S.  Department 
of  Agriculture,  Washington,  D.C.  :  — 

Farmer's  Bulletin  No.  47,  Insects  affecting  the  Cotton  Plant; 
No.  59,  Bee  Keeping ;  No.  70,  The  Principal  Insect  Enemies  of 
the  Grape ;  No.  80,  The  Peach  Twig 
Borer ;  No.  99,  Three  Insect  Enemies 
of  Shade  Trees;  No.  120,  The  Principal 
Insects  affecting  the  Tobacco  Plant ; 
No.  127,  Important  Insecticides;  No. 
132,  The  Principal  Insect  Enemies  of 
Growing  Wheat;  No.  145,  Carbon  Bi- 
sulphid  as  an  Insecticide ;  No.  146, 
Insecticides  and  Fungicides;  No.  152, 
revised,  Mange  in  Cattle;  No.  153,  Orchard  Enemies  in  the 
Pacific  Northwest;  No.  155,  How  Insects  affect  Health  in  Rural 
Districts;  No.  159,  Scab  in  Sheep;  No.  165,  Silkworm  Culture; 
No.  171,  The  Control  of  the  Codling  Moth;  No.  172,  Scale  In- 
sects and  Mites  on  Citrus  Trees;  No.  196,  Usefulness  of  the 
Toad  ;  No.  209,  Controlling  the  Boll  Weevil  in  Cotton  Seed  and 
at  Ginneries  ;  No.  211,  The  Use  of  Paris  Green  in  controlling  the 

Cotton  Boll  Weevil ;  No.  212, 
The  Cotton  Bollworm ;  No. 
216,  The  Control  of  the  Boll 
Weevil;  No.  223,  Miscellane- 
ous Cotton  Insects  in  Texas  ; 
No.  247,  The  Control  of  the 
Codling  Moth  and  Apple  Scab. 
The  following  bulletins  of 
the  Bureau  of  Entomology  may 
be  obtained  from  the  same  source  at  the  prices  affixed  :  Bulletin 
No.  25  (old  series),  Destructive  Locusts,  15c;  No.  1  (new  series), 
The  Honey  Bee,  15c.  ;  No.  3,  The  San  Jose  Scale,  10c. ;  No.  4, 
The  Principal  Household  Insects  of  the  U.  S.,  10c. ;  No.  11,  The 
Gypsy  Moth  in  America,  5c. ;  No.  14,  The  Periodical  Cicada, 
15c;  No.  15,  The  Chinch  Bug,  10c. ;  No.  16,  The  Hessian  Fly, 
10c. ;  Nos.  19,  23,  and  t,^,  Insects   Injurious   to  Vegetables,    10c. 


FIG.  185. —  Female  plant  louse,  with  and 
without  wings  (enlarged). 


96 


ANIMAL   BIOLOGY 


each;  No.  25,  Notes  on  Mosquitoes  of  the  U.  S.,  10c. ;  No.  42 
Some  Insects  attacking  the  Stems  of  Growing  Wheat,  Rye,  Barley, 

and    Oats,   5c. ;    No.   50,   The 
Cotton  Bolhvorm,  25c. ;  No.  51, 


The  Mexican  Boll  Weevil,  »>5c. 
Bureau  of  Plant  Industry  — 
Bulletin  No.  88,  Weevil-resisting 
Adaptations  of  the  Cotton  Plant, 
ioc.     This  gives  an  instructive 

account  of  the  struggle  of  a  plant  for  existence  against  an  insect 

enemy. 


FIG.  186.  —  Gall  fly  (enlarged)  and  oak 
gall  with  larva,  and  one  from  which 
a  developed  insect  has  escaped. 


Fig.  187.  — Plan  of  Mouth  Parts  of  the  Insect  Orders.  A,  straight 
wings,  nerve  wings,  false  nerve  wings  ;  B,  joined  wings ;  C,  scaly  wings ;  D,  half 
wings  ;  E,  two  wings. 

ol,  upper  lip;  ok,  biting  jaws;  uk,  holding  jaws;   ul,  under  lip;   kt,  jaw  fingers;  It,  lip  fingers 


y 


vm.  M-. 


--    £ 


CHAPTER  IX 


MOLLUSKS 


The  Fresh-water  Mussel 

Suggestions.  —  The  mussel  is  usually  easy  to  procure  from 
streams  and  lakes  by  raking  or  dredging.  In  cities  the  hard- 
shelled  clam,  or  quahog,  is  for  sale  at  the  markets,  and  the  follow- 
ing descriptions  apply  to  the  anodon,  unio,  or  quahog,  with 
slight  changes  in  regard  to  the  siphons.  Mussels  can  be  kept 
alive  for  a  long  time  in  a  tub  with  sand  in  the  bottom.  Pairs  of 
shells  should  be  at  hand  for  study. 

External  Features. — The  shell  is  an  elongated  oval, 
broader  and  blunter  at  one  end  (Fig.  188).  Why  does 
the  animal  close  its  shell  ?  Does  it  open  the  shell  ? 
Why?  Does  it  thrust  the  foot  forward  and  pull  up  to  it, 
or  thrust  the  foot  back  and  push?  (Mussels  and  clams 
have  no  bones. )  Does  it  go  with  the  blunt  or  the  more 
tapering  end  of  the  shell  forward?  (Fig.  188.)  Can  a 
mussel  swim  ?  Why,  or  why  not  ? 
h  97 


98 


ANIMAL   BIOLOGY 


Fig.  iE 


■Anodon,  or  fresh-water 
mussel. 


shells  for  valves  in  pumps. 


Lay  the  shells,  fitted  together,  in  your  hand  with  the  hinge 
side  away  from  you  and  the  blunt  end  to  the  left  (Fig.  188). 

Is  the  right  or  the  left  shell 
uppermost  ?  Which  is  the 
top,  or  dorsal,  side  ?  Which 
is  the  front,  or  anterior, 
end  ?  Is  the  straight  edge 
at  the  top  or  the  bottom  ? 
Our  word  "  valve  "  is  derived 
from  a  word  meaning  shell, 
because  the  Romans  used 
Is  the  mussel  a  univalve  or  a 
bivalve  ?     Which  kind  is  the  oyster  ?     The  snail  ? 

Does  the  mussel  have  bilateral  symmetry  ?  Can  you 
find  a  horny  covaing,  or  epidermis,  over  the  limy  shell 
of  a  fresh  specimen  ?  Why  is  it  necessary  ?  Does  water 
dissolve  lime  ?  Horn  ?  Find  a  bare  spot.  Does  any  of 
the  shell  appear  to  be  missing  there  ? 

The  bare  projection  on  each  shell  is  called  the  umbo. 
Is  the  umbo  near  the  ventral  or  the  dorsal  line  ?  The 
posterior  or  anterior  end  ?  Is 
the  surface  of  the  umbones 
worn  ?  Do  the  umbones  rub 
against  the  sand  as  the  mussel 
plows  its  way  along  ?  How  are 
the  shells  held  together  ?  Where 
is  the  ligament  attached  ?  (Fig. 
189.)  Is  it  opposite  the  um- 
bones or  more  to  the  front  or 
rear?  (Fig.  189.)  Is  the  liga- 
ment of  the  same  material  as  the  shell?  Is  the  ligament 
in  a  compressed  condition  when  the  shell  is  open  or  when 
it  is  closed?     (Fig.  189.)     When  is  the  muscle  relaxed? 


Fig.  189.  —  Diagram  of  Shell 
open  and  closed,  showing  mus- 
cle, m,  and  ligament,  b. 


MOLLUSKS 


99 


Fig.  190. —  Mussel  crawl- 
ing in  sand. 


Notice  the  lines  on  the  outside  of  the  shell  (Figs.  188 
and  190).  What  point  do  they  surround?  They  are  lines 
of  growth.  Was  each  line  once  the 
margin  of  the  shell  ?  If  the  shell 
should  increase  in  size,  what  would 
the  present  margin  become?  (Fig. 
191.)  Does  growth  take  place  on 
the  margin  only?  Did  the  shell 
grow  thicker  as  it  grew  larger? 
Where  is  it  thinnest  ? 

Draw  the  outside  of  the  shell  from 
the  side.  Draw  a  dorsal  view.  By  the  drawings  write  the 
names  of  the  margins  of  the  shell  (p.  98)  and  of  other  parts 
learned,  using  lines  to  indicate  the  location  of  the  parts. 

Study  the  surface  of  the  shell  inside  and  out.  The 
inside  is  called  mother-of-pearl.  Is  it  of  lime  ?  Is  the 
deeper  layer  of  the  shell  of  lime  ?  (When  weak  hydro- 
chloric acid  or  strong  vinegar  is  dropped  on  limy  substances, 
a  gas,  carbon  dioxid,  bubbles  up.)  Compare  the  thickness 
of  the  epidermal  layer,  the  middle  clialky  layer,  and  the 
inner,  pearly  layer. 

Anatomy  of  the  Mussel.  —  What  parts  protrude  at  any 
time  beyond  the  edge  of  the  shell  ?     (Fig.  190.)     The  shell 


?ri.W  w 


is  secreted  by  two  folds  of  the  outer 
layer  of  the  soft  body  of  the  mus- 
sel. These  large,  flaplike  folds  hang 
down  on  each  side,  and  are  called 
the  mantle.  The  two  great  flaps 
of  the  mantle  hang  down  lower  than 
the  rest  of  the  body  and  line  the 
shell  which  it  secretes  (Fig.  192). 
The  epidermis  of  the  mantle  secretes  the  shell  just  as  the 
epidermis  of  the  crawfish  secretes  its  crust.     Can  you  find 


ra.i 

Fig.  191.  —  Diagram. 
Change  of  points  of  attach- 
ment of  muscles  as  mussel 
enlarges.     (Morgan.) 


IOO 


ANIMAL   BIOLOGY 


NTESTIKC 
CELOM 


Fig.  192.  — Cross  Section 
of  Mussel.  (Diagram, 
after  Parker.) 


the  pallial  line,  or  the  line  to  which  the  mantle  extended 
on  each  shell  when  the  animal  was  alive?  A  free  portion 
of  the  mantle  extended  like  a  fringe  below  the  pallial  line. 

The  shells  were  held  together  by- 
two  large  adductor  ptuscles.  The 
anterior  adductor  (Fig.  193)  is  near 
the  front  end,  above  the  foot.  The 
posterior  adductor  is  toward  the  rear 
end,  but  not  so  near  the  end  as  the 
anterior.  Can  you  find  both  muscle 
scars  in  the  shells  ?  Are  they  nearer 
the  ventral  or  dorsal  surface  ?  The 
points  of  attachment  traveled  down- 
ward and  farther  apart  as  the  ani- 
mal grew  (see  Fig.  191).  Higher 
than  the  larger  scars  are  small  scars,  or  impressions,  where 
the  protractor  and  retractor  muscles  that  extend  and  draw 
in  the  foot  were  attached. 

The  muscular/i?^/  extends  downward  in  the  middle,  half- 
way between  the  shells  (Fig.  193).  On  each  side  of  the 
foot  and  behind 


it  hang  down 
the  two  pairs  of 
gills,  the  outer 
pair  and  the  in- 
ner pair  (Fig. 
192).  They  may 
be  compared  to 
four  V-shaped 
troughs  with 
their  sides  full  of  holes.     The  water  enters  the  troughs 


POST?  ADD"  MUS. 


Fig.  193.  —  Anatomy  of  Mussel.    (Beddard.) 


through  the  holes  and  overflows  above.    Is  there  a  marked 
difference  in  the  size  of  the  two  pairs  of  gills  ?     A  kind  of 


UNIVERSITY  J 

Of  J 


MOLLUSKS 


IOI 


chamber  for  the  gills  is  made  by  the  joining  of  the  mantle 
flaps  below,  along  the  ventral  line.  The  mantle  edges  are 
separated  at  two  places,  leaving  openings  called  exhalent 
and  inhalent  siphons. 

Fresh  water  with  its  oxygen,  propelled  by  cilia  at  the 
opening  and  on  the  gills,  enters  through  the  lower  or 
inhalent  siphon,  passes  between  the  gills,  and  goes  to  an 
upper  passage,  leaving  the  gill  chamber  by  a  slit  which 
separates  the  gills  from  the  foot. 
For  this  passage,  see  arrow 
(Fig.  194).  The  movement  of 
the  water  is  opposite  to  the  way 
the  arrow  points.  After  going 
upward  and  backward,  the  water 
emerges  by  the  exhalent  siphon. 
The  gills  originally  consisted  of 
a  great  number  of  filaments. 
These  are  now  united,  but  not 
completely  so,  and  the  gills  still 
have  a  perforated  or  lattice 
structure.  Thus  they  present  a 
large  surface  for  absorbing  oxy- 
gen from  the  water. 

The  mouth  is  in  front  of  the  foot 
anterior  adductor  muscle  (Fig.  194). 


Fig.  194.  —  Mussel. 

A,  left  shell  and  mantle  flap  removed. 
B,  section  through  body. 
Question:  Guided  by  other  figures, 
identify  the  parts   to  which  lines  are 
drawn. 


between  it  and  the 
On  each  side  of  the 
mouth  are  the  labial  palps,  which  are  lateral  lips  (Fig.  195). 
They  have  cilia  which  convey  the  food  to  the  mouth  after 
the  inhalent  siphon  has  sent  food  beyond  the  gill  chamber 
and  near  to  the  mouth.  Thus  both  food  and  oxygen  enter 
at  the  inhalent  siphon.  The  foot  is  in  the  position  of  a 
lower  lip,  and  if  regarded  as  a  greatly  extended  lower  lip, 
the  animal  may  be  said  to  have  what  is  to  us  the  absurd 
habit  of  using  its  lower  lip  as  a  foot.     The  foot  is  some- 


102 


AXIMAL   BIOLOGY 


times  said  to  be  hatchet-shaped  (Fig.  195).  Do  you  see 
any  resemblance  ?  Does  the  foot  penetrate  deep  or  shal- 
low into  the  sand  ?  (Fig.  190.)  Why, 
or  why  not  ? 

The  food  tube  of  the  mussel  is  com- 
paratively simple.  Behind  the  mouth  it 
enlarges  into  a  swelling  called  the  stom- 
ach (Fig.  193).  The  bile  ducts  of  the 
neighboring  liver  empty  into  the  stomach. 
The  intestine  makes  several  turns  in  the 
substance  of  the  upper  part  of  the  foot, 
and  then  passing  upward,  it  runs  ap- 
proximately straight  to  the  vent  (or  anus), 
which  is  in  the  wall  of  the  exhalent 
siphon.  The  intestine  not  only  runs 
through  the  pericardial  cavity  (celonie) 
surrounding  the  heart,  but  through  the 
ventricle  of  the  heart  itself  (Fig.  196). 
The  kidneys  consist  of  tubes  which 
open  into  the  pericardial  chamber  above 
and  into  the  gill  chamber  below  (Neph., 
Fig.  193).  The  tubes  are  surrounded  by 
numerous  blood  vessels  (Fig.  198)  and 
carry  off  the  waste  matter  from  the  blood. 
The  nervous  system  consists  of  three 
pairs  of  ga?ig/ia  and  nerves  (Fig.  197). 
The  ganglia  are  distinguishable  because  of 
their  orange  color.  The  pedal 
ganglia  on  the  front  of  the  foot 
are  easily  seen  also ;  the  vis- 
ceral ganglia  on  the  posterior 
adductor  muscle  may  be  seen 
without    removing    the    mussel 

from  the  shell  (Fig.  193).  The  reproductive  organs 
open  into  the  rear  portion  of  the  gill  cavity  (Fig.  193). 
The  sperms,  having  been  set  free  in  the  water,  are  drawn  into 
the  ova  by  the   same  current   that  brings  the   food.     The   eggs 


FIG.  195.—  Missel.  From 
below.  Level  cut  across 
both  shells. 

Se,  palp;  P,  foot;  O,  mouth; 
G,  liver;  Gg,  Vg,  Pg,  gan- 
glia. 


Fig.  196.  —  Heart  of 
Mi  SSEL,  with  intestine 
passing  through  it. 


Fig.  197. 


MOLL  USKS 


103 


are  hatched  in  the  gills.     After  a  while  the  young  mussels  go  out 
through  the  siphon. 

Summary. —  In  the  gills  (Fig.  198)  the  blood  gains  what? 
Loses  what?  From  the  digestive  tube  the  blood  absorbs  nourish- 
ment. In  the  kidneys  the  blood  is  partly  purified  by  the  loss  of 
nitrogenous  waste. 


The  cilia  of  the  fringes  on  the  inhalent,  or  lower,  siphon, 
vibrate  continually  and  drive  water  and  food  particles  into 
the  mouth  cavity.  Food  particles  that  are  brought  near  the 
labial  palps  are  conveyed  by  them  si 

to  the  mouth.  As  the  water  passes 
along  the  perforated  gills,  its  oxygen 
is  absorbed  ;  the  mantle  also  absorbs 
oxygen  from  the  water  as  it  passes. 
The  water,  as  stated  before,  goes 
next  through  a  passage  between  the 
foot  and  palp  into  the  cavity  above 
the  gills  and  on  out  through  the  ex- 
halent  siphon.  By  stirring  the  water, 
or  placing  a  drop  of  ink  near  the  /. 

siphons  of  a  mussel  kept  in  a  tub,    Fig.    198.  —  Diagram    of 

..!•.•  r  -L.    a  i  Mussel      cut      across, 

the  direction  01  its  now  may  be  seen.        ,     .  „    „„,,    _     .,, 

J  showing  mantle,  ma  ;  gills, 

The    pulsations    of    the    heart    are       kie;  foot,/;  heart,  k;  in- 
plainly  visible  in  a  living  mollusk. 

Habits  of  the  Mussel.  —  Is  it  abundant  in  clear  or  muddy 
water ;  swift,  still,  or  slightly  moving  water  ?  Describe 
its  track  or  furrow.  What  is  its  rate  of  travel  ?  Can  you 
distinguish  the  spots  where  the  foot  was  attached  to  the 
ground  ?  How  long  is  one  "  step  "  compared  to  the  length 
of  the  shell  ?  The  animal  usually  has  the  valves  opened 
that  it  may  breathe  and  eat.  The  hinge  ligament  acts  like 
the  case  spring  of  a  watch,  and  holds  the  valves  open  un- 
less the  adductor  muscles  draw  them  together  (Fig.  189). 


104 


ANIMAL   BIOLOGY 


When  the  mussel  first  hatches  from  the  egg,  it  has  a  tri- 
angular shell.     It  soon  attaches  itself  to  some  fish  and  thus 
travels    about ;    after    two    months   it 
drops  to  the  bottom  again. 

Other  Mollusca.  —  The  oyster  s  shells 
are  not  an  exact  pair,  the  shell  which 
lies  upon  the  bottom  being  hollowed 
out  to  contain  the  body,  and  the  upper 
shell  being  flat.  Can  you  tell  by  ex- 
amining an  oyster  shell  which  was  the 
lower  valve  ?  Does  it  show  signs  of 
having  been  attached  to  the  bottom  ? 
The  young  oyster,  like  the  young  mus- 
sel, is  free-swimming.  Like  the  arthropoda,  most  mollusks 
undergo  a  metamorphosis  to  reach 
the  adult  stage  (Fig.  199). 

Examine  the  shells  of  clams, 
snails,  scallops,  and  cockles.  Make 
drawings  of  their  shells.  The  slug 
is  very  similar  to  the  snail  except 
that  it  has  no  shell.  If  the  shell  of  the  snail  shown  in 
Fig.  202  were  removed,  there  would  be  left  a  very  good 

representation  of  a  slug. 


Fig.  199.  —  Oyster. 

C,  mouth;  a,  vent;  g,g', 
ganglia;  mt,  mantle;  b, 
gill. 


Fig.  200.  —  Trochus. 


Economic  Importance  of 
Mollusca.  —  Several  species 
of  clams  are  eaten.  One  of 
them  is  the  Jiard-sJicll  clam 
(quahog)  found  on  the  At- 
lantic coast  from  Cape  Cod 
to  Texas.  Its  shell  is  white.  It  often  burrows  slightly 
beneath  the  surface.  The  soft-shell  clam  is  better  liked  as 
food.  It  lives  along  the  shores  of  all  northern  seas.  It 
burrows  a  foot  beneath  the  surface  and  extends  its  siphons 


M  1  smm^ 


Fig.  201.  —  Cypr^ea.     (Univalve, 
with  a  long  opening  to  shell.) 


MOLLUSKS 


105 


through  the  burrow  to  the  surface  when  the  tide  is  in, 
and  draws  into  its  shell  the  water  containing  animalcules 
and  oxygen. 

Oysters  to  the  value  of  many  millions  of  dollars  are  gath- 
ered and  sold  every  year.  The  most  valuable  oyster  fish- 
eries of  the  United  States  are  in  Chesapeake  Bay.  The 
young  oysters,  or  "  spat,"  after  they  attach  themselves  to 
the  bottom  in  shallow  water,  are  transplanted.  New  oyster 
beds  are  formed  in  this  way.  The  beds  are  sometimes 
strewn  with  pieces  of  rock,  broken  pottery,  etc.,  to  encourage 
the  oysters  to  attach  themselves.  The  dark  spot  in  the 
fleshy  body  of  the  oyster  is  the  digestive  gland,  or  liver. 
The  cut  ends  of  the  tough  adductor  muscles  are  noticeable 
in  raw  oysters.  The  starfish  is  very  destructive  in  oyster 
beds. 

Pearls  are  deposited  by  bivalves  around  some  irritating 
particle  that  gets  between  the  shell  and  the  mantle.  The 
pearl  oyster  furnishes  most  of  the  pearls ;  sometimes 
pearls  of  great  value  are  obtained  from  fresh-water  mussels 
in  the  United 
States.  Name 
articles  that  are 
made  partly  or 
wholly  of  mother- 
of-pearl. 

Study  of  a  Live 
Snail  or  Slug.  —  Is 
its  body  dry  or 
moist  ?     Do     land 

snails  and  slugs  have  lungs  or  gills?  Why?  How  many  pairs 
of  tentacles  has  it?  What  is  their  relative  length  and  position? 
The  eyes  are  dark  spots  at  bases  of  tentacles  of  snail  and  at  the 
tips  of  the  rear  tentacles  of  slug.  Touch  the  tentacles.  What 
happens?     Do  the  tentacles  simply  stretch,  or  do  they  turn  inside 


Fig.  202. —  A  Snail. 

/,  mouth:  vf,  hf,  feelers;  e,  opening  of  egg  duct;  fit,  foot; 
via,  mantle;  In,  opening  to  lung;  a,  vent. 


io6 


ANIMAL   BIOLOGY 


out  as  they  are  extended?      Is  the  respiratory  opening  on  the 

right  or  left  side  of  the  body  ?    On  the  mantle  fold  or  on  the  body? 

(Figs.  202-3-4.)     How 

often  does  the  aperture 

open  and  close  ? 

Place    the   snail    in   a 
Fig.  203.  — A  Slug.  .  ,  ,  T^ 

11101st     tumbler.       Does 

the  whole  under  surface  seem  to  be  used  in  creeping?  Does  the 
creeping  surface  change  shape  as  the  snail  creeps  ?  Do  any  folds 
or  wrinkles  seem  to 
move  either  toward  the 
front  or  rear  of  its 
body?  Is  enough  mu- 
cus left  to  mark  the 
path  traveled?  The 
fold  moves  to  the  front, 
adheres,  and  smooths 
out  as  the  slug  or  snail 
is  pulled  forward. 

Cephalopods.  —  The 
highest  and  best  de- 
veloped mollusks  are 
the  cephalopods,  or  "  head-footed  "  mollusks.  Surrounding  the 
mouth  are  eight  or  ten  appendages  which  serve  both  as  feet  and 
as  arms.  These  appendages  have  two  rows  of  sucking  disks  by 
which  the  animal  attaches  itself  to  the  sea  bottom,  or  seizes  fish 
or  other  prey  with  a  firm  grip.     The  commonest  examples  are  the 

squid,  with  a  long  body  and  ten 
arms,  and  the  octopus,  or  devil- 
fish, with  a  short  body  and 
eight  arms.  Cephalopods  have 
strong  biting  mouth  parts  and 
complex  eyes  somewhat  resem- 
bling the  eyes  of  backboned, 
or  vertebrate,  animals.  The 
large  and  staring  eyes  add  to  the  uncanny,  terrifying  appearance. 

The  sepia  or  "  ink  "  discharged  through  the  siphon  of  the  squid 
makes   a   dark   cloud  in   the    water  and  favors  its  escape  from 


Fig.  204.  - 


•Circulation  and  Respiration 
in  Snail. 

a,  mouth;  b,  h,  foot;   c.  vent;   d,  d,  lung;  h,  heart. 
Blood  vessels  are  black.     (Perrier.) 


Fig.  205.  — A  Squid. 


MOLLUSKS 


IO7 


enemies  almost  as 
much  as  its  swiftness 
(Fig.  205).  The  squid 
sometimes  approaches 
a  fish  with  motion  so 
slow  as  to  be  imper- 
ceptible, and  then  sud- 
denly seizes  it,  and 
quickly  kills  it  by  bit- 
ing it  on  the  back  be- 
hind the  head. 

The  octopus  is  more 
sluggish  than  the  squid. 
Large  species  called 
devilfish  sometimes  have  a  spread  of  arms  of  twenty-five  feet. 
The  pearlx  nautilus  (Fig.  206)  and  the  female  of  the  paper  argo- 
naut (Fig.  207)  are  examples  of  cephalopods  that  have  shells. 
The  cuttlefish  is  closely  related  to  the  squid. 


Fig.  206. —  Pearly  Nautilus.  (Shell  sawed 
through  to  show  chambers  used  when  it  was 
smaller,  and  siphuncle,  S,  connecting  them.  Ten- 
tacles, T.) 


Fig.  207.— Paper  Argonaut  (female). 

x  Vis  {i.e.  the  animal   is  three  times  as  long 

and  broad  as  figure) . 


Fig.  208. —  Paper  Argo- 
naut (male),     x  i/2. 


General  Questions.  —  The  living  parts  of  the  mussel  are 
very  soft,  the  name  mollusca  having  been  derived  from 
the  Latin  word  mollis,  soft.  Why  is  it  that  the  softest 
animals,  the  mollusks,  have  the  hardest  coverings  ? 

To  which  class  of  mollusks  is  the  name  acephala  (head- 
less) appropriate  ?     Lamellibranchiata  (platelike  gills)  ? 


io8 


ANIMAL   BfOLOGY 


Why  is  a  smooth  shell  suited  to  a  clam  and  a  rough 
shell  suited  to  an  oyster  ?  Why  are  the  turns  of  a  snail's 
shell  so  small  near  the  center? 

Why  does  the  mussel  have  no  use  for  head,  eyes,  or  pro- 
jecting feelers?  In  what  position  of  the  valves  of  a  mussel 
is  the  hinge  ligament  in  a  stretched  condition  ?  How  does 
the  shape  of  the  mussel's  gills  insure  that  the  water  cur- 
rent and  blood  current  are  brought  in  close  contact  ? 

The  three  classes  of  mollusks  are :  the  pelecypoda 
(hatchet-footed);  gastropoda  (stomach-footed);  and  cepha- 
lopoda (head-footed).     Give  an  example  of  each  class. 

Comparison  of  Mollusks 


Mussel 

Snail 

Squid 

Shell 

Head 

Body 

Foot 

Gills 

Eyes 

Comparative  Review.  —  (To  occupy  an  entire  page  in  notebook.) 

Grass- 
hopper 

Spider 

Crayfish 

Centipede 

Mussel 

Bilateral    or  radiate 

Appendages   for   lo- 
comotion 

Names   of   divisions 
of  body 

Organs  and  method 
of  breathing 

Locomotion 

CHAPTER   X 


FISHES 


studied. 


Suggestions. — 

The  behavior  of  a 

live    fish    in    clear 

water,  preferably  in 

a  glass  vessel  or  an 

aquarium,  should  be 

A  skeleton  may  be 

prepared  by  placing  a  fish  in 

the  reach  of  ants.     Skeletons 

of  animals  placed  on  ant  beds 

are   cleaned  very  thoroughly. 

The  study  of  the  perch,  that  follows,  will  apply  to  almost  any 

common  fish. 

Movements  and  External  Features.  —  What  is  the  gen- 
eral shape  of  the  body  of  a  fish  ?  How  does  the  dorsal,  or 
upper,  region  differ  in  form  from  the  ventral  ?  Is  there  a 
narrow  part  or  neck  where  the  head  joins  the  trunk? 
Where  is  the  body  thickest  ?  What  is  the  ratio  between 
the  length  and  height  ?  (Fig.  209.)  Are  the  right  and  left 
sides  alike  ?  Is  the  symmetry  of  the  fish  bilateral  or 
radial  ? 

The  body  of  the  fisli  may  be  divided  into  three  regions, 
—  the  head,  trunk,  and  tail.  The  trunk  begins  with  the 
foremost  scales ;  the  tail  is  said  to  begin  at  the  vent,  or 
anus.  Which  regions  bear  appendages?  Is  the  head 
movable  independently  of  the  trunk,  or  do  they  move 
together  ?  State  the  advantage  or  disadvantage  in  this. 
Is  the  body  depressed  (flattened  vertically)  or  compressed 

109 


I  IO 


ANIMAL    BIOLOGY 


(flattened  laterally)?  Do  both  forms  occur  among  fishes? 
(See  figures  on  pages  123,  124.) 

How  is  the  shape  of  the  body  advantageous  for  move- 
ment t  Can  a  fish  turn  more  readily  from  side  to  side,  or 
up  and  clown  ?  Why  ?  Is  the  head  wedge-shaped  or  coni- 
cal ?  Are  the  jaws  flattened  laterally  or  vertically  ?  The 
fish  swims  in  the  water,  the  bird  swims  in  the  air.  Account 
for  the  differences  in  the  shape  of  their  bodies. 

Is  the  covering  of  the  body  like  the  covering  of  any  ani- 
mal yet  studied  ?     The  scales  are  attached  in  little  pockets, 


^ 


"^T^-f'^-r 


Stb 


wr 


FIG.  209. —  WHITE  PERCH   (Morone  Americana). 

or  folds,  in  the  skin.  Observe  the  shape  and  size  of  scales 
on  different  parts  of  the  body.  What  parts  of  the  fish  are 
without  scales  ?  Examine  a  single  scale ;  what  is  its 
shape  ?  Do  you  see  concentric  lines  of  growth  on  a  scale  ? 
Sketch  a  few  of  the  scales  to  show  their  arrangement. 
What  is  the  use  of  scales  ?  Why  are  no  scales  needed  on 
the  head  ?  How  much  of  each  scale  is  hidden  ?  Is  there 
a  film  over  the  scale  ?  Are  the  colors  in  the  scale  or 
on  it  ? 

The  Fins.  —  Are  the  movements  of  the  fish   active   or 
sluggish  ?     Can  it  remain  stationary  without  using  its  fins  ? 


FISHES  1 1 1 

Can  it  move  backward  ?  How  are  the  fins  set  in  motion  ? 
What  is  the  color  of  the  flesh,  or  muscles,  of  a  fish  ?  Count 
the  fins.  How  many  are  in  pairs  ?  (Fig.  209.)  How  many 
are  vertical  ?  How  many  are  on  the  side  ?  How  many 
are  on  the  middle  line  ?  Are  the  paired  or  unpaired  fins 
more  effective  in  balancing  the  fish  ?  In  turning  it  from 
side  to  side?  In  raising  and  lowering  the  fish?  In  pro- 
pelling it  forward?  How  are  some  of  the  fins  useful  to 
the  fish  besides  for  balancing  and  swimming  ? 

The  hard  spines  supporting  the  fins  are  called  the  fin 
rays.  The  fin  on  the  dorsal  line  of  the  fish  is  called  the 
dorsal  fin.  Are  its  rays  larger  or  smaller  than  the  rays  of 
the  other  fins  ?  The  perch  is  sometimes  said  to  have  two 
dorsal  fins,  since  it  is  divided  into  two  parts.  The  fin 
forming  the  tail  is  called  the  tail  fin,  or  caudal  fin.  Are 
its  upper  and  lower  corners  alike  in  all  fishes  ?  (Fig.  228.) 
On  the  ventral  side,  just  behind  the  vent,  is  the  ventral 
fin,  also  called  the  anal  fin.  The  three  fins  mentioned  are 
unpaired  fins.  Of  the  four-paired  fins,  the  pair  higher  on 
the  sides  (and  usually  nearer  the  front)  are  the  pectoral 
fins.  The  pair  nearer  the  ventral  line  are  the  pelvic  fins. 
They  are  close  together,  and  in  many  fish  are  joined 
across  the  ventral  line.  The  ventral  fins  are  compared  to 
the  legs,  and  the  pectoral  fins  to  the  arms,  of  higher  verte- 
brates.    (Fig.  244.)     Compare  fins  of  fish,  pages  123,  124. 

Make  a  drawing  of  the  fish  seen  from  the  side,  omit- 
ting the  scales  unless  your  drawing  is  very  large. 

Are  the  eyes  on  the  top  or  sides  of  the  head,  or  both  ? 
Can  a  fish  shut  its  eyes  ?  Why,  or  why  not  ?  Is  the  eye- 
ball bare,  or  covered  by  a  membrane  ?  Is  the  covering  of 
the  eyeball  continuous  with  the  skin  of  the  head  ?  Is 
there  a  fold  or  wrinkle  in  this  membrane  or  the  surround- 
ing skin  ?     Has  the  eye  a  pupil  ?     An  iris  ?     Is  the  eye  of 


112 


ANIMAL  BIOLOGY 


Fig.  210.  —  Blackboard  Outline  of  Fish. 


the  fish  immovable,  slightly  movable,  or  freely  movable  ? 
Can  it  look  with  both  eyes  at  the  same  object?  Is  the 
range  of  vision  more  upward  or  downward  ?     To  the  front 

or  side  ?  In  what 
direction  is  vision 
impossible  ?  Can  a 
fish  close  its  eyes 
in  sleep  ?  Does 
the  eyeball  appear 
spherical  or  flat- 
tened in  front  ? 
The  ball  is  really 
spherical,  the  lens  is  very  convex,  and  fish  are  nearsighted. 
Far  sight  would  be  useless  in  a  dense  medium  like  water. 

In  what  direction  are  the  nostrils  from  the  eyes?  (Fig. 
211.)  There  are  two  pairs  of  nostrils,  but  only  one  pair  of 
nasal  cavities,  with  two  nostrils  opening  into  each.  There 
are  no  nasal  passages  to  the  mouth,  -. 

as  the  test  with  a  probe  shows 
that  the  cavities  do  not  open  into 
the  mouth.  What  two  functions 
has  the  nose  in  man  ?  What  func- 
tion has  it  in  the  fish  ? 

There  are  no  external  ears. 
The  ear  sacs  are  embedded  in  the 
bones  of  the  skull.  Is  hearing  acute  or  dull  ?  When  fish- 
ing, is  it  more  necessary  not  to  talk  or  to  step  lightly, 
so  as  not  to  jar  the  boat  or  bank  ? 

What  is  the  use  of  the  large  openings  found  at  the  back 
of  the  head  on  each  side  ?  (Fig.  211.)  Under  the  skin  at 
the  sides  of  the  head  are  thin  membrane  bones  formed  from 
the  skin  ;  they  aid  the  skin  in  protection.  Just  under  these 
membrane  bones  are  the  gill  covers,  of  true  bone.     WThich 


Fig.  211.  — Head  of  Carp. 


FISHES  1 1 3 

consists  of  more  parts,  the  membranous  layer,  or  the  true 
bony  layer  in  the  gill  cover  ?     (Figs.  21 1  and  212.) 

Is  the  mouth  large  or  small  ?  Are  the  teeth  blunt  or 
pointed  ?  Near  the  outer  edge,  or  far  in  the  mouth  ? 
(Fig.  212.)  Does  the  fish  have  lips?  Are  the  teeth  in 
one  continuous  row  in  either  jaw  ?  In  the  upper  jaw 
there  are  also  teeth  on  the  premaxillary  bones.  These 
bones  are  in  front  of  the  maxillary  bones,  which  are  with- 
out teeth.  Teeth  are  also  found  in  the  roof  of  the  mouth, 
and  the  tongue  bears  horny  appendages  similar  to  teeth. 
Are  the  teeth  of  the  fish  better  suited  for  chewing  or  for 


■.MMkJ^ 


-Js^ 


Fig.  212.  —  Skeleton  of  Perch. 

grasping  ?  Why  are  teeth  on  the  tongue  useful  ?  Watch 
a  fish  eating :  does  it  chew  its  food  ?  Can  a  fish  taste  ? 
Test  by  placing  bits  of  brown  paper  and  food  in  a  vessel 
or  jar  containing  a  live  fish.  Is  the  throat,  or  gullet,  of  the 
fish  large  or  small  ? 

The  skeleton  of  a  fish  is  simpler  than  the  skeleton  of 
other  backboned  animals.  Study  Fig.  212  or  a  prepared 
skeleton.  At  first  glance,  the  skeleton  appears  to  have 
two  vertebral  columns.  Why  ?  What  bones  does  the  fish 
have  that  correspond  to  bones  in  the  human  skeleton  ? 
Are  the  projections  (processes)  from  the  vertebrae  long  or 
short  ?  The  ribs  are  attached  to  the  vertebrae  of  the  trunk, 
the  last  rib  being  above  the  vent.  The  tail  begins  at  the 
1 


H4 


ANIMAL   BIOLOGY 


vent.  Are  there  more  tail  vertebrae  or  trunk  vertebrae? 
Are  there  any  neek  (cervical)  vertebrae  {i.e.  in  front  of 
those  that  bear  ribs)?  The  first  few  ribs  (how  many  ?)  are 
attached  to  the  central  body  of  the  vertebrae.     The  re- 

S,  rf. 


Fig.  213. 

maining  ribs  are  loosely  attached  to  processes  on  the 
vertebrae.  The  ribs  of  bony  fishes  are  not  homologous 
with  the  ribs  of  the  higher  vertebrates.  In  most  fishes 
there  are  bones  called  intermuscular  bones  attached  to  the 
first  ribs  (how  many  in  the  perch  ?)  which  are  possibly  homol- 
ogous to  true  ribs ;  that  is,  true  ribs  in  the  higher  verte- 
brates may  have  been  developed  from  such  beginnings. 

Which,  if  any,  of  the  fin  skeletons  (Fig.  214)  are  not 
attached  to  the  general  skeleton?  Which  fin  is  composed 
chiefly  of  tapering,  pointed  rays  ?     Which  fins  consist  of 

rays     which     sub- 
divide   and   widen 


Fig.  214. —  Soft-rayed  and  Spiny-rayed  Fins. 


toward  the  end  ? 
Which  kind  are 
stiff,  and  which  are 
flexible?  Which  of 
the  fin  rays  are  segmented,  or  in  two  portions  ?  The  outer 
segment  is  called  the  radial,  the  inner  the  basal  segment. 
Which  segments  are  longer  ?  There  is  one  basal  segment 
that  lacks  a  radial  segment;  find  it  (Fig.  212). 


FISHES 


115 


Fig.  215.  —  Carp,  with 
right  gill  cover  removed 
to  show  gills. 


What  is  the  advantage  of  the  backbone  plan  of  struc- 
ture over  the  armor-plate  plan  ?  You  have  seen  the  spool- 
like body  of  the  vertebra  in  canned  salmon.  Is  it  concave, 
flat,  or  convex  at  the  ends  ? 

The  gills  are  at  the  sides  of  the  head  (Fig.  215)  under 
the  opercula,  or  gill  covers.  What  is  the  color  of  the  gills  ? 
Do  the  blood  vessels  appear  to  be 
very  near  the  surface  of  the  gills,  or 
away  from  the  surface  ?  What  advan- 
tage in  this  ?  Are  the  gills  smooth 
or  wrinkled?  (Fig.  215.)  What  ad- 
vantage ?  The  bony  supports  of  the 
gills,  called  the  gill  arches,  are  shown 
in  Fig.  216  {kx  to  k4).  How  many 
arches  on  each  side?  The  gill  arches  have  projections 
on  their  front  sides,  called  gill  rakers,  to  prevent  food 
oS  from  being  washed 

through  the  clefts 
between  the  arches. 
The  fringes  on  the 
rear  of  the  gill 
arches  are  called 
the  gill  filaments  (a, 
Fig.  216).  These 
filaments  support 
the  thin  and  much- 
wrinkled  borders  of 
the  gills,  for  the 
gills  are  constructed 
on  the  plan  of  exposing  the  greatest  possible  surface  to 
the  water.  Compare  the  plan  of  the  gills  and  the  human 
lungs.  The  gill  opening  on  each  side  is  guarded  by 
seven  rays  (kk,  Fig.  216)  along  the  hinder  border  of  the 


Fig.  216.  — Skeleton  around  Throat  of  Fish. 


u6 


ANIMAL  BIOLOGY 


gill  cover.     These  rays  grow  from  the  tongue  bone.     {Zn, 

Fig.  216.     This  is  a  rear  view.) 

Watch  a  live  fish  and  determine  how  the  water  is  forced 

between  the  gills.  Is  the  mouth  opened  and  closed  in  the 
act  of  breathing  ?  Are  the  openings  behind 
the   gill   covers    opened    and    closed  ?     How 


Fig.  217.— 

Circulation 

in  Gills. 


Fig.  218.  —  Nostrils,  Mouth,  and  Gill  Openings  of 
Sting- ray. 


many  times  per  minute  does  fresh  water  reach 
the  gills  ?  Do  the  mouth  and  gill  covers 
open  at  the  same  time  ?  Why  must  the  water 
in  contact  with  the  gills  be  changed  constantly  ?  Why 
does  a  fish  usually  rest  with  its 
head  up  stream  ?  How  may  a 
fish  be  kept  alive  for  a  time 
after  it  is  removed  from  the 
water  ?  Why  does  drying  of 
the  gills  prevent  breathing  ?  If 
the  mouth  of  a  fish  were  propped  open,  and  the  fish  re- 
turned to  the  water,  would  it  suffocate  ?    Why,  or  why  not  ? 

Food  Tube.  —  The  gullet  is  short  and  wide.  The  stomach  is 
elongated  (Fig.  220).  There  is  a  slight  constriction,  or  narrow- 
ing, where  it  joins  the  intestine.  Is  the  intestine  straight,  or  does 
it  lie  in  few  or  in  many  loops?  (Fig.  220.)  The  liver  has  a  gall 
bladder  and  empties  into  the  intestine  through  a  bile  duct.    Is  the 


Fig.  219. 


Gill  Openings  of 
Eel. 


FISHES 


117 


liver  large  or  small?  Simple  orlobed?  The  spleen  {mi,  Fig.  220) 
lies  in  a  loop  of  the  intestine.  The  last  part  of  the  intestine  is 
straight  and  is  called  the  rectum.  Is  it  of  the  same  size  as  the 
other  portions  of  the  intestine?  The  fish  does  not  possess  a  pan- 
creas, the  most  important  digestive  gland  of  higher  vertebrates. 


Fig.  220.  —  Anatomy  of  Carp.    (See  also  colored  figure  4.) 

bf,  barbels  on  head  (for  feeling) ;  h,  ventricle  of  heart;  as,  aortic  bulb  for  regulating  flow  to 
gills;  vk,  venous  sinus:  ao,  dorsal  aorta;  ma,  stomach;  /.liver;  gb,  gall  cyst;  mi,  spleen; 
d,  small  intestine;  »id,  large  intestine;  a,  vent;  s,  s,  swim  bladder;  ni,ni,  kidney;  hi, 
ureter;  hb,  bladder:   ro,  eggs  (roe\;   mke,  opening  of  ducts  from  kidney  and  ovary. 

Questions  :  Are  the  kidneys  dorsal  or  ventral  ?  The  swim  bladder  ?  Why  ?  Why  is  the 
swim  bladder  double  ?     Does  blood  enter  gills  above  or  below  ? 

The  ovary  lies  between  the  intestine  and  the  air  bladder.  In  Fig. 
220  it  is  shown  enlarged  and  filled  with  egg  masses  called  roe.  It 
opens  by  a  pore  behind  the  vent.  The  silver  lining  of  the  body  cavity 
is  called  the  peritoneum.     (See  Chap.  VII.  Human  Biology.) 

Is  the  air bladder  simple  or  partly  divided  in  the  perch?  In  the  carp? 
(Fig.  220.)  Is  it  above  or  below  the  center  of  the  body?  Why?  The 
air  bladder  makes  the  body  of  the  fish  about  as  light  as  water  that  it 
may  rise  and  sink  with  little  effort.  When  a  fish  dies,  the  gases  of 
decomposition  distend  the  bladder  and  the  abdomen,  and  the  fish  turns 
over.     Why? 

Where  are  the  kidneys?  (Fig.  220.)  Their  ends  unite  close  under 
the  spinal  column.  The  ureters,  or  tubes,  leading  from  them,  unite, 
and  after  passing  a  small  urinary  bladder,  lead  to  a  tiny  urinary  pore 
just  behind  the  opening  from  the  ovary.     (Colored  figure  4.) 

The  Circulation.  —  The  fish,  unlike  other  vertebrates,  has  its 
breathing  organs  and  its  heart  in  its  head.  The  gills  have  already 
been  described.     The  heart  of  an  air-breathing  vertebrate  is  near 


n; 


ANIMAL   BIOLOGY 


its  lungs.  Why?  The  heart  of  a  fish  is  near  its  gills  for  the  same 
reason.  The  heart  has  one  auricle  and  one  ventricle.  (Colored 
figure  i.) 

Blood  returning  to  the  heart  comes  through  several  veins  into  a 
sinus,  or  antechamber,    whence  it    passes  down  through  a  valve 


Fig.  221.— Plan  ok  Circulation. 

Ab,  arteries  to  gills;   Ba,  aortic  bulb;    /',  ventricle. 

into  the  auricle ;  from  the  auricle  it  goes  forward  into  the  ventricle. 

The  ventricle  sends  it  into  an  artery,  not  directly,  but  through  a 
bulb  (as,  Fig.  220),  which  serves  to  maintain 
a  steady  flow,  without  pulse  beats,  into  the 
large  artery  (aorta)  leading  to  the  gills.  The 
arteries  leading  from  the  gills  join  to  form  a 
dorsal  aorta  (Ao,  Fig.  221),  which  passes 
backward,  inclosed  by  the  lower  processes  of 
the  spinal  column.  After  going  through  the 
capillaries  of  the  various  organs,  the  blood 
returns  to  the  heart  through  veins. 

The  color  of  the  blood  is  given  by  red 
corpuscles.  These  are  nucleated,  oval,  and 
larger  than  the  blood  corpuscles  of  other  ver- 
tebrates. The  blood  of  the  fish  is  slightly 
above  the  temperature  of  the  water  it  in- 
habits. 

Notice  the  general  shape  of  the  brain 
(Fig.  222).  Are  its  subdivisions  distinct  or 
indistinct?  Are  the  lobes  in  pairs?  The 
middle   portion   of  the   brain  is   the   widest, 

and  consists  of  the  two  optic  lobes.     From  these  lobes  the  optic 

nerves  pass  beneath  the  brain  to  the  eyes  (Sn,  Fig.  223).     In 


Fig.  222. —  Brain  of 
Perch,  from  above. 

n,  end  of  nerve  of  smell ; 
au,  eye;  v,  s,  w,  fore, 
mid,  and  hind  brain; 
h,  spinal  bulb;  r,  spi- 
nal cord. 


FISHES 


119 


front  of  the  optic  lobes  lie  the  two  cerebral  lobes,  or  the  cerebrum. 
The  small  olfactory  lobes  are  seen  (Fig.  224)  in  front  of  the  cere- 
brum. The  olfactory  nerves  may  be  traced  to'  the  nostrils.  Back 
of  the  optic  lobes  (mid  brain)  is  the  cerebellum  (hind  brain),  and 

back  of  it  is  the  medulla  oblongata, 
or  beginning  of  the  spinal  cord. 


Fig.  224. —  Brain  of  Perch, 
from  below. 


Fig.  223. 


-Brain  of  Perch, 
side  view. 


Taking  the  eyeball  for  comparison,  is  the  whole  brain  as  large 
as  one  eyeball  ?  (Fig.  222.)  Judging  from  the  size  of  the  parts  of 
the  brain,  which  is  more  important  with  the  fish,  thinking  or  per- 
ception?    Which  is  the  most  important  sense? 

The  scales  along  a  certain  line  on  each  side  of  the  fish,  called 
the  lateral  line,  are  perforated  over  a  series  of  lateral  line  sense 
organs,  supposed  to  be  the  chief  organs  of  touch  (see  Fig.  209). 

Questions.  —  Which  of  the  fins  of  the  fish  have  a  use 
which  corresponds  to  the  keel  of  a  boat  ?   The  rudder  ?    A 


Mm  -- 


ijEj£^ 


Fig.  225.— The  Stickleback.  Instead  of  depositing  the  eggs  on 
the  bottom,  it  makes  a  nest  of  water  plants—  the  only  fish  that  does 
so  —  and  bravely  defends  it. 


120 


ANIMAL  BIOLOGY 


Fig.  226. —  Artificial  Fecundation.  The 
egg-cells  and  sperm-cells  are  pressed  out  into 
a  pan  of  water. 


paddle  for  sculling  ? 
An  oar?  State  several 
reasons  why  the  head 
of  the  fish  must  be 
very  large,  although 
the  brain  is  very  small. 
Does  all  the  blood  go 
to  the  gills  just  after 
leaving  the  heart  ? 

Make  a  list  of  the 
different    species    of 
fish     found     in     the 
waters  of  your  neigh- 
borhood ;  in  the  markets  of  your  town. 

Reproduction. —  The  female  fish  deposits  the  unfertilized 
eggs,  or  ova,  in  a  secluded  spot  on  the  bottom.  Afterward 
the  male  fish  deposits  the  sperms  in  the  same  place  (see 
Fig.  225).  The  eggs,  thus  unprotected,  and  newly  hatched 
fish  as  well,  are  used  for  food  by  fish  of  the  same  and  other 
species.  To  compensate  for  this  great  destruction,  most 
fish  lay  (spawn)  many  thousands  of  eggs,  very  few  of 
which  reach  maturity.  Higher  vertebrates  {e.g.  birds)  have, 
by  their  superior  in- 
telligence, risen  above 
this  wasteful  method 
of  reproduction.  Some 
kinds  of  marine  fish, 
notably  cod,  herring, 
and  salmon,  go  many 
miles  up  fresh  rivers 
to  spawn.  It  is  possible  that  this  is  because  they  were 
originally  fresh-water  species ;  yet  they  die  if  placed  in 
fresh  water  except  during  the  spawning  season.     They  go 


Fig.  227.  — Newly  hatched  Trout,  with 
yolk-sac  adhering,  eyes  large,  and  fins  mere 
folds  of  the  skin.     (Enlarged.) 


FISHES 


121 


because  of  instinct,  which  is  simply  an  inherited  habit. 
Rivers  may  be  safer  than  the  ocean  for  their  young.  They 
are  worn  and  exhausted  by  the  journey,  and  never  survive 
to  lay  eggs  the  second  time. 


Fig.  228.  —  A  Shark  {Acanthias  vulgaris). 

The  air  bladder  is  developed  from  the  food  tube  in  the 
embryo  fish,  and  is  homologous  with  lungs  in  the  higher 
vertebrates.     Are  their  functions  the  same  ? 

Fish  that  feed  on  flesh  have  a  short  intestine.  Those 
that  eat  plants  have  a  long  intestine.  Which  kind  of  food 
is  more  quickly  digested  ? 

There  are  mucous  glands  in  the  skin  of  a  fish  which 
supply  a  secretion  to  facilitate  movement  through  the 
water ;  hence  a  freshly  caught  fish,  before  the  secretion 
has  dried,  feels  very  slippery. 

The  air  bladder,  although  homologous  to  lungs,  is  not  a 
breathing  organ  in  common  fishes.  It  is  filled  by  the 
formation  of  gases  from  the  blood,  and  can  be  made 
smaller  by  the  contraction  of  muscles  along  the  sides  of 
the  body ;  this  causes  the  fish  to  sink.  In  the  gar  and 
other  ganoids,  the  air  bladder  contains  blood  vessels,  is  con- 
nected with  the  gullet,  and  is  used  in  breathing.  Organs 
serving  the  same  purpose  in  different  animals  are  said  to  be 
analogous.  To  what  in  man  are  the  gills  of  the  fish  analo- 
gous ?  Organs  having  a  like  position  and  origin  are 
said  to  be  homologous.  The  air  bladders  of  a  fish  are 
homologous  with  the  lungs  of  man  ;  but  since  they  have 
not  the  same  use  they  are  not  analogous. 


122 


AX  I. MA  I.    BIOLOGY 


How  does  the  tail  of  a  shark  or  a  gar  differ  from  the 
tail  of  common  fishes?  (Fig.  228.)  Do  you  know  of  fish 
destitute  of  scales?  Do  you  know  of  fish  with  whiplike 
feelers  on  the  head  ?  (Figs.)  Why  are  most  fishes  white 
on  the  under  side  ? 


Comparative  Review.  —  (Copy  table  on  one  page  or  two  facing  pages 
f  notebook.) 


I-    THERE 
A    HEAD? 

A  Xeck? 

Method  of 
Feeding 

Digestive 

Organs  and 

Digestion 

Reproduc- 
tion- 

Senses 

Ameba 

Sponge 

Hydra 

Starfish 

Earthworm 

Wasp 

Mussel 

Fish 

Kig.  229. —  Drawing  the  Seine. 


Fig.  234.  —  Turbot. 


Fig.  239.  —  Salmon. 


Seven  Food  Fish.    Three  Curious  Fish. 
Special  Reports.      (Encyclopedia,  texts,  dictionary.) 

123 


Fig.  243.  —  Lantern  Fish  (Linophtyne  lucifer).  (After  Collett. ) 


Fig.  240.— 
Ska  Horse 
{hippocampus) , 
with  incubat- 
ing pouch,  Brt. 


Fig.  244.  —  Lung  Fish  of  Australia 
(Cera/odus  miolepis). 


Fig.  242.  —  Torpedo.  Elec- 
trical organs  at  right  and 
left  of  brain. 


Fig.  246.  —  Seaweed  Fish,    x^ 
(Pkyllopteryx  eg  ties) . 


Remarkable  Fish.    Special  Reports.    (Encyclopedia,  texts,  dictionary.) 

124 


GENERAL    CLASSIFICA  TION 


125 


KEY   TO   THE    BRANCHES,   OR   SUB-KINGDOMS 


Aj  One-celled  Animals  {Protozoans) 
A.,    Many-celled  Animals  {Metazoans) 

Bj  Radiate  (around  a  center).  Without 
head :  all  aquatic,  resembling  plants,  and 
often  fixed  to  bottom 

C\  Walls  of  body  serving  as  digestive 
organs 

D1  Many  openings,  no  tentacles 

D2  One    opening,   which   is    both 
mouth    and    vent ;    tentacles    for 
seizing  prey 
C,  Digestive    tube   distinct   from  body 
wall,  spiny  skin 
B2  Bilateral.   With  anterior  and  posterior 
end  ;  dorsal  and  ventral  surface 

Cl  Body  of  successive  segments ;    legs 

without  joints 
C2  External     skeleton     of     successive 

rings ;  jointed  legs 
C3  Body    soft ;     no    skeleton ;    usually 

bearing  a  limy  shell 
C4  Internal   jointed  skeleton,   attached 
to  an  axis  or  vertebral  column 


I.  Protozoans 


II.  Sponges 

(Port/era) 

III.  Polyps 

(  Ccelenteratd) 

IV.  ECHINODERMS 


V.  Vermes 
VI.  Arthropods 
VII.   Mollusks 
VIII.  Vertebrates 


Examples.  —Tell  the  branch  to  which  each  of  the  following  animals 
belongs :  crayfish,  earthworm,  thousand  leg,  white  grub,  sea  anemone, 
ameba,  tapeworm,  caterpillar,  beetle,  sparrow,  snake,  oyster,  starfish, 
fish.     Be  prepared  to  state  the  reason  for  each  classification. 

The  classes  in  the  branch  vertebrata  are:  1.  Fishes  (pisces). 
2.  Frogs  and  Salamanders  (batrachia).  3.  Reptiles  (reptilia). 
4.    Birds  (aves).     5.    Mammals  {mammalia). 


Fig.  247.— A  Snail.     (Which  branch  ?    Why?) 


CHAPTER  XI 

BATRACHIA 

The  theory  of  evolution  teaches  that  animal  life  began  in  a  very 
simple  form  in  the  sea,  and  that  afterward  the  higher  sea  animals 
lost  their  gills  and  developed  lungs  and  legs  and  came  out  to  live 
.  upon  the  land ;  truly  a  marvelous  procedure,  and  incredible  to 
many,  although  the  process  is  repeated  every  spring  in  count- 
less instances  in  pond  and  brook. 

In  popular  language,  every  cold-blooded  vertebrate  breathing 
with  lungs  is  called  a  reptile.  The  name  reptile  is  properlv 
applied  only  to  lizards,  snakes,  turtles,  and  alligators.  The  com- 
mon mistake  of  speaking  of  frogs  and  salamanders  as  reptiles 
arises  from  considering  them  only  in  their  adult  condition.  Rep- 
tiles hatch  from  the  egg  as  tiny  reptiles  resembling  the  adult 
forms ;  frogs  and  salamanders,  as  every  one  knows,  leave  the  egg 
in  the  form  of  tadpoles  (Fig.  248).  The  fact  that  frogs  and 
salamanders  begin  active  life  as  fishes,  breathing  by  gills,  serves  to 
distinguish  them  from  other  cold-blooded  animals,  and  causes 
naturalists  to  place  them  in  a  separate  class,  called  batrachia 
(twice  breather)   or  amphibia  (double  life). 

Tadpoles 

Suggestions.  — Tadpoles  may  be  studied  by  placing  a  number 
of  frog's  eggs  in  a  jar  of  water,  care  being  taken  not  to  place 
a  large  number  of  eggs  in  a  small  amount  of  water.  When  they 
hatch,  water  plants  {e.g.  green  algae)  should  be  added  for  food. 
The  behavior  of  frogs  may  be  best  studied  in  a  tub  of  water.  A 
toad  in  captivity  should  be  given  a  cool,  moist  place,  and  fed  well. 
A  piece  of  meat  placed  near  a  toad  may  attract  flies,  and  the  toad 
may  be  observed  while  catching  them,  but  the  motion  is  so  swift 
as  to  be  almost  imperceptible.  Live  flies  may  be  put  into  a  glass 
jar  with  a  toad.     Toads  do  not  move  about  until  twilight,  except 

126 


BA  TKA  CHI  A 


127 


in  cloudy,  wet  weather.  They  return  to  ponds  and  brooks  in 
spring  at  the  time  for  laying  eggs.  This  time  for  both  frogs  and 
toads  is  shown  by  trilling.  All  frogs,  except  tree  frogs,  remain  in 
or  near  the  water  all  the  year. 


Fig.  248.  — Metamorphoses  of  the  Frog,  numbered  in  order. 

Do  eggs  hatch  and  tadpoles  grow  more  rapidly  in  a 
jar  of  water  kept  in  a  warm  place  or  in  a  cold  place  ? 
In  pond  water  or  drinking  water  ?  Can  the  tadpoles  be 
seen  to  move  in  the  eggs  before  hatching  ?  When  do 
the  external  gills  show  ?     (Fig.  248.) 

What  parts  may  be  described  in  a  tadpole  ?  What  is 
the  shape  of  the  tail  ?  Compare  the  tadpole  with  the  fish 
as  to  (1)  general 
shape,  (2)  cover- 
ing, (3)  fins,  (4) 
tail,  (5)  gills. 

Do  the  exter- 
nal gills  disap- 
pear before  or  after  any  rudiments  of  limbs  appear  ? 
(6,  7,  Fig.  248.)  Can  you  locate  the  gills  after  they  be- 
come internal  ?     (Fig.  249.) 


Fig.  249.  —  Tadpole,  from  below,  showing  intestine 
and  internal  gills.     (Enlarged.) 


128  ANIMAL   BIOLOGY 

Iii  what  state  of  growth  are  the  legs  when  the  tadpole 
first  goes  to  the  surface  to  breathe  ?  Which  legs  appear 
first  ?  What  advantage  is  this  ?  What  becomes  of  the 
tail  ?  Is  the  tail  entirely  gone  before  the  frog  first  leaves 
the  water  ?  Are  tadpoles  habitually  in  motion  or  at 
rest  ? 

Is  the  intestine  visible  through  the  skin?  (Fig.  249.) 
Is  it  straight  or  coiled  ?  Remembering  why  some  fish 
have  larger  intestines  than  others,  and  that  a  cow  has  a 
long  intestine  and  a  cat  a  short  one,  state  why  a  tad- 
pole has  a  relatively  longer  intestine  than  a  frog. 

Compare  the  mouth,  jaws,  eyes,  skin,  body,  and  habits 
of  tadpole  mid  frog. 

Frogs 

Prove  that  frogs  and  toads  are  beneficial  to  man.  Did 
you  ever  know  of  a  frog  or  toad  destroying  anything 
useful,  or  harming  any  one,  or  causing  warts  ?  How 
many  pupils  in  class  ever  had  warts  ?  Had  they  handled 
frogs  before  the  warts  came  ?  Frogs  are  interesting, 
gentle,  timid  animals.  Why  are  they  repulsive  to  some 
people  ? 

Environment.  —  Where  are  frogs  found  in  greatest 
numbers  ?  What  occurs  when  danger  threatens  them  ? 
What  enemies  do  they  have  ?  What  color,  or  tint,  is  most 
prominent  on  a  frog  ?  Does  the  color  "  mimic  "  or  imi- 
tate its  surroundings  ?  What  is  the  color  of  the  under 
side  of  the  body  ?  (Fig.  250.)  Why  is  there  greater 
safety  in  that  color  ?  What  enemies  would  see  water  frogs 
from  below  ?  Do  tree  frogs  mimic  the  bark  ?  The 
leaves  ? 

Can  a  frog  stay  under  water  for  an  indefinite  time  ? 
Why,  or  why  not?       What    part  of  a  frog  is  above  the 


BATRACHIA 


129 


surface  when  it  floats  or  swims  in  a  tub  of  water  ?  Why  ? 
Do  frogs  croak  in  the  water  or  on  the  bank  ?  Why  do 
they  croak  after  a  rain  ?     Do  toads  croak  ? 

Are  the  eggs  laid  in  still  or  flowing  water  ?  In  a  clear 
place  or  among  sticks  and  stems  ?  Singly,  or  in  strings  or 
in  masses?  (Fig.  248.)  Describe  an  egg.  Why  do  frogs 
dig  into  the  mud  in  autumn  in  cold  climates  ?  Why  do 
they  not  dig  in  mud  at  the  bottom  of  a  pond  ?  Why  is 
digging  unnecessary  in  the  Gulf  states  ? 


Fig.  250.  —  Painted  Frog  {Chorophilus  ornatus),  of  Mexico. 

Describe  the  position  of  the  frog  when  still  (Fig.  250). 
What  advantage  in  this  position  ?  Does  the  frog  use 
its  fore  legs  in  swimming  or  jumping?  Its  hind  legs? 
How  is  the  frog  fitted  for  jumping  ?  Compare  it  in  this 
respect  with  a  jumping  insect;  a  jumping  mammal.  How 
is  it  fitted  for  swimming  ?  Is  the  general  build  of  its  body 
better  fitted  for  swimming  or  jumping?  How  far  can  a 
frog  jump  ? 

External  Features.  —  The  frog  may  be  said  to  have  two 
regions  in  its  body,  the  head  and  trunk.     A  neck  hardly 


130  ANIMAL  BIOLOGY 

exists,  as  there  is  only  one  vertebra  in  front  of  the  shoul- 
ders (Fig.  252),  although  most  vertebrates  have  seven  neck 
(cervical)  vertebrae.  There  are  no  tail  (caudal)  vertebrae, 
even  in  the  tadpole  state  of  frogs  and  toads. 

The  head  appears  triangular  in  shape  when  viewed  from 
what  direction  ?  The  head  of  a  frog  is  more  pointed  than 
the  head  of  a  toad.  Is  the  skull  a  closed  case  of  broad 
bones  or  an  open  structure  of  narrow  bones  ?     (Fig.  252.) 

Describe  the  mouth.     Observe  the  extent  of  the  mouth 

opening  (Fig.  251).     Axe.  teeth  present  in  the  upper  jaw? 

The  lower  jaw  ?     Are  the  teeth  sharp  or  dull  ?     Does  the 

^  ^^^^^^        _         frog  chew  its  food  ?     Is  the  tongue 

f0^^^^'M'/'''"  slender  or  thick  ?     (Fig.   251.)     Is 

^g^aw^Tp^-  ^-"°^g"-T  it  attached  to  the  front  or  the  back 

Y^xviiff^* W-^      °f  *-ne  mouth?      la  what  direction 

L ■'■>;r.]T/^  does  the  free  end  extend  when  the 

xljjf  tongue  lies  flat  ?    Is  the  end  pointed 

or  lobed  ?     How  far   out   will   the 
Fig.  251.  — Head  of  Frog. 

tongue    stretch  ?      For    what    is    it 

used  ?  Why  is  it  better  for  the  teeth  to  be  in  the  upper 
jaw  rather  than  in  the  lower  jaw?  That  the  teeth  are  of 
little  service  is  shown  by  the  fact  that  the  toad  with  simi- 
lar habits  of  eating  has  no  teeth.  Will  a  toad  catch  and 
swallow  a  bullet  or  pebble  rolled  before  it  ?  The  toad  is 
accustomed  to  living  food,  hence  prefers  a  moving  insect 
to  a  still  one. 

The  Senses.  —  Compare  the  eyes  with  the  eyes  of  a 
fish  in  respect  to  position  and  parts.  Are  the  eyes  pro- 
truding or  deep-set  ?  Touch  the  eye  of  a  live  frog.  Can 
it  be  retracted  ?  What  is  the  shape  of  the  pupil  ?  The 
color  of  the  iris  ?  Is  the  eye  bright  or  dull  ?  What 
probably  gave  rise  to  the  superstition  that  a  toad  had  a 
jewel    in    its    head?     Is  there    a   third  eyelid?     Are  the 


B  ATRAC  HI  A 


131 


upper  and  lower  eyelids  of  the  same  thickness  ?  With 
which  lid  does  it  wink  ?     Close  its  eye  ? 

Observe  the  large  oval  ear  drum  or  tympanum.  What 
is  its  direction  from  the  eye?  (Fig.  251.)  The  mouth? 
Is  there  a  projecting  ear?  Does  the  frog  hear  well? 
What  reason  for  your  answer  ?  As  in  the  human  ear,  a 
tube  (the  Eustachian  tube)  leads  from  the  mouth  to  the 
inner  side  of  the  tympanum. 

How  many  nostrils?  (Fig.  251.)  Are  they  near  to- 
gether or  separated  ?  Large  or  small  ?  A  bristle  passed 
into  the  nostril  comes  into  the  mouth  not  far  back  in  the 
roof.     Why  must  it  differ  from  a  fish  in  this  ? 

How  do  the  fore  and  kind  legs  differ  ?  How  many  toes 
on  the  fore  foot  or  hand  ?  On  the  hind  foot  ?  On  which 
foot  is  one  of  the  toes  rudimentary  ?  Why  is  the  fore  limb 
of  no  assistance  in  propelling  the  body  in  jumping  ?  Do 
the  toes  turn  in  or  out?  (Fig.  250.)  How  does  the  frog 
give  direction  to  the 


jump  ?  What  would 
be  the  disadvantage 
of  always  jumping 
straight  forward 
when  fleeing?  Which 
legs  are  more  useful 
in  alighting  ? 

Divisions  of  the 
Limbs.  —  Distinguish 
the  upper  arm,  fore- 
arm, and  hand  in  the 
fore  limb  (Figs.  252  and  253).  Compare  with  skeleton  of 
man  (Fig.  399).  Do  the  arms  of  a  man  and  a  frog  both 
have  one  bone  in  the  upper  arm  and  two  in  the  forearm  f 
Both  have  several  closely  joined  bones  in  the  wrist  and 


Fig.  252. —  Skeleton'  of  Frog. 


\$2 


AX1MAL   BIOLOGY 


five  separate  bones  in  the  palm.     Do  any  of  the  frog's 
fingers  have  three  joints  ?     Compare  a/so  the  /eg  of  man 

and  the  hind  leg 
of  the  frog  (Figs. 
253  and  399).  Does 
the  thigh  have  one 
bone  in  each  ?  The 
shank  of  man  has 
two  bones,  shin  and 
splint  bone.  Do 
you  see  a  groove 
near  the  end  in  the 
shank  bone  of  a 
frog  (Fig.  252),  in- 
dicating that  it 
was  formed  by  the 
union  of  a  shin  and 
splint  bone  ?  The 
first  two  of  the  five  bones  of  the  ankle  are  elongated,  giv- 
ing the  hind  leg  the  appearance  of 
having  an  extra  joint  (Fig.  253).  The 
foot  consists  of  six  digits,  one  of  which, 
like  the  thumb  on  the  fore  limb,  is 
rudimentary.  The  five  developed  toes 
give  the  five  digits  of  the  typical  verte- 
brate foot.  Besides  the  five  bones  cor- 
responding to  the  instep,  the  toes  have 
two,  three,  or  four  bones  each.  How 
is  the  hind  foot  specialized  for  swim- 
ming? Which  joint  of  the  leg  con- 
tains most  muscle?  (Fig.  254.)  Find  other  bones  of  the 
frog  analogous  in  position  and  similar  in  form  to  bones  in 
the  human  skeleton. 


Fig.  253.  — Skeleton  of  Frog. 


Fig.  254. —  Leg  Mus- 
cles of  Frog. 


BATRACHIA 


133 


Is  the  skin  of  a  frog  tight  or  loose  ?  Does  it  have  any 
appendages  corresponding  to  scales,  feathers,  or  hair  of 
other  vertebrates  ?  Is  the  skin  rough  or  smooth  ?  The 
toad  is  furnished  with  glands  in  the  skin  which  are  some- 
times swollen  ;  they  form  a  bitter  secretion,  and  may  be, 
to  some  extent,  a  protection.  Yet  birds  and  snakes  do  not 
hesitate  to  swallow  toads  whole.  Show  how  both  upper 
and  under  surfaces  of  frog  illustrate  protective  coloration. 

All  batrachians  have  large  and  numerous  blood  vessels 
in  the  skin  by  which  gases  are  exchanged  with  the  air, 
the  skin  being  almost  equal  to  a  third  lung.  That  the 
skin  may  function  in  this  way,  it 
must  not  become  dry.  Using  this 
fact,  account  for  certain  habits  of 
toads  as  well  as  frogs. 

If  a  frog  is  kept  in  the  dark  or 
on  a  dark  surface,  its  skin  will  be- 
come darker  than  if  kept  in  the  light 
or  on  a  white  dish.  Try  this  experi- 
ment, comparing  two  frogs.  This 
power  of  changing  color  is  believed 
to  be  due  to  the  diminution  in  size 
of  certain  pigment  cells  by  contrac- 
tion, and  enlargement  from  relaxation. 
This  power  is  possessed  to  a  certain 
degree  not  only  by  batrachians  but 
also  by  many  fishes  and  reptiles. 
The  chameleon,  or  green  lizard  of 
the  Gulf  states,  surpasses  all  other 
animals  in  this  respect  (Fig.  280). 
What  advantage  from  this  power  ? 

Digestive  System.  —  The  large  mouth  cavity  is  connected 
by  a  short  throat  with  the  gullet,  or  esophagus  (Fig.  255). 


Fig.  255.  — Digestive 
Canal  of  Frog. 

Mh,  mouth;  Z,  tongue  pulled 
outward;  S1.  opening  to 
larynx;  Oe,  gullet;  M,  stom- 
ach; D,  intestine;  P,  pan- 
creas; L,  liver;  G,  gall 
bladder;  R,  rectum;  Hb, 
bladder;  CI,  cloaca;  A, 
vent. 


134 


ANIMAL   BIOLOGY 


A  slit  called  the  glottis  opens  from  the  throat  into  the 
lungs  (Fig.  255).  Is  the  gullet  long  or  short?  Inroad 
or  narrow?  Is  the  stomach  short  or  elongated?  Is  the 
division  distinct  between  the  stomach  and  gullet,  and 
stomach  and  intestine  ?  Is  the  liver  large  or  small  ?  Is 
it  simple  or  lobed  ?  The  pancreas  lies  between  the 
stomach  and  the  first  bend  of  the  intestines  (Fig.  255). 
What  is  its  shape  ?     A  bile  duct  connects  the  liver  with 

the  small  intestine  (Dc,  Fig. 
255).  It  passes  through  the 
pancreas,  from  which  it  re- 
ceives several  pancreatic 
ducts.  After  many  turns,  the 
small  intestine  joins  the  large 
intestine.  The  last  part  of 
the  large  intestine  is  called 
the  rectum  (Latin,  straight). 
The  last  part  of  the  rectum  is 
called  the  cloaca  (Latin,  a 
drain),  and  into  it  the  ducts 
from  the  kidneys  and  repro- 
ductive glands  also  open.  The 
kidneys  are  large,  elongated, 
and  flat.  They  lie  under  the 
dorsal  wall.  The  urinary  bladder  is  also  large.  Does  the 
salamander  have  a  similar  digestive  system?  (Fig.  256.) 
Why  are  the  liver  and  lungs  (Fig.  256)  longer  in  a  sala- 
mander than  in  a  frog  ? 

Respiration.  —  How  many  lungs?  Are  they  simple 
or  lobed  ?  (Fig.  256.)  A  lung  cut  open  is  seen  to  be 
baglike,  with  numerous  ridges  on  its  inner  surface. 
This  increases  the  surface  with  which  the  air  may  come 
in    contact.     In    the    walls    of    the    lungs    are    numerous 


Fig.  256.- 


■  Anatomy  of  Sala- 
mander. 

la,  heart;  5,lungs;  5  «,  stomach;  3  b,  in 
testine;  j  c,  large  intestine;  4,  liver 
8,  egg  masses;  10,  bladder;  M,  vent. 


BATRACHIA 


135 


capillaries.  Does  the  frog  breathe  with  mouth  open  or 
closed?  Does  the  frog  have  any  ribs  for  expanding  the 
chest  ?  What  part  of  the  head  expands  and  contracts  ? 
Is  this  motion  repeated  at  a  slow  or  rapid  rate  ?  Regu- 
larly or  irregularly  ?  There  are  valves  in  the  nostrils  for 
opening  and  closing  them.  Is  there  any  indication  of 
opening  and  closing  as  the  throat  expands  and  contracts  ? 
The  mouth  and  throat  (pharynx)  are  filled  with  air  each 
time  the  throat  swells,  and  the  exchange  of  gases  (which 
gases  ?)  takes  place  continually  through  their  walls  and 
the  walls  of  the  lungs.  At  intervals  the  air  is  forced 
through  the  glottis  into  the  lungs.  After  a  short  time 
it  is  expelled  from  the  lungs  by  the  muscular  abdominal 
walls,  which  press  upon  the  abdominal  organs,  and  so 
upon  the  lungs.  Immediately  the  air  is  forced  back 
into  the  lungs,  so  that  they  are  kept  filled.  In  some 
species  the  lungs  regularly  expand  at  every  second  con- 
traction of  the  throat.  This  is  shown  by  a  slight  out- 
ward motion  at  the  sides.  Does  the  motion  of  the  throat 
cease  when  the  frog  is  under  water  ?  Why  would  the 
frog  be  unable  to  breathe  (except  through  the  skin)  if  its 
mouth  were  propped  open  ?  Why  does  the  fact  that  the 
breathing  is  so  slow  as  to  almost  cease  when  hibernat- 
ing, aid  the  frog  in  going  through  the  winter  without 
starving?  (Chap.  I.)  Why  must  frogs  and  toads  keep  their 
skins  moist?     Which  looks  more  like  a  clod?     Why? 

The  Heart  and  Circulation.  —  What  is  the  shape  of  the  heart? 
(Fig.  257.)  Observe  the  two  auricles  in  front  and  the  conical 
ventricle  behind  them.  The  great  arterial  trunk  from  the  ventricle 
passes  forward  beyond  the  auricles ;  it  divides  into  two  branches 
which  turn  to  the  right  and  left  (Fig.  257).  Each  branch  im- 
mediately subdivides  into  three  arteries  (Fig.  257),  one  going  to 
the  head,  one  to  the  lungs  and  skin,  and    a   third,  the  largest, 


136 


ANIMAL   BIOLOGY 


passes  backward   in   the  trunk,    where  it  is  united  again  to  its 

fellow.     (Colored  Fig.  2.) 

Both  of  the  pulmonary  veins,  returning  to  the  heart  with  pure 

blood  from  the  lungs,  empty  into  the  left  auricle.     Veins  with  the 

impure  blood  from  the  body  empty  into  the  right  auricle.     Both 

the  auricles  empty  into  the  ventri- 
cles, but  the  pure  and  impure  blood 
are  prevented  from  thoroughly  mix- 
ing by  ridges  on  the  inside  of  the 
ventricle.  Only  in  an  animal  with 
a  four-chambered  heart  does  pure 
blood  from  the  lungs  pass  unmixed 
and  pure  to  all  parts  of  the  body, 


fEM-y 

Fig.  257.  —  Plan  of  Frog's 
Circulation. 

Venous  system  is  black;    the  arterial, 

white.     A  U,  auricles;    V,  ventricle; 

L,  lung;   Z.//',  liver.    Aorta  has  one  FlG.   258.  —  FROG'S  BLOOD    (magnified  2500 

branch  to  right,  another  to  left,  which  areas).      Red     cells    oval,    nucleated,    and 

reunite  below.     Right  branch    only  ]arger  than  human  blood  cells.      Nuclei  of 

persists  in  birds,  left  branch  in  beasts  twQ  whUe  ce]Js  yisible  near  centen      (pea. 

and  man.  ,      ,     „ 

body.) 

and  only  such  animals  are  warm-blooded.    The  purer  {i.e.  the  more 
oxygenated)  the  blood,  the  greater  the  oxidation  and  warmth. 

The  red  corpuscles  in  a  frog's  blood  are  oval  and  larger  than  those 
of  man.  Are  all  of  them  nucleated?  (Fig.  258.)  The  flow  of  blood  in 
the  web  of  a  frog's  foot  is  a  striking  and  interesting  sight.  It  may 
be  easily  shown  by  wrapping  a  small  frog  in  a  wet  cloth  and  laying 
it  with  one  foot  extended  upon  a  glass  slip  on  the  stage  of  a 
miscroscope. 


BA  TEA  CHI  A 


137 


The  brain  of  the  frog  (Fig.  259)  is  much  like  that  of  a  fish 
(Fig.  224).  The  olfactory,  cerebral,  and  optic  lobes,  cerebellum 
and  medulla  are  in  the  same  relative  position,  although  their  rela- 
tive sizes  are  not  the  same.     Compared  with  the 

other    parts,    are   the 

olfactory  lobes   more 

or      less      developed 

than  in  a  fish?     The 

cerebral  hemispheres  ? 

The  optic  lobes?  The 

cerebellum?  There  is 

a  cavity  in  the  brain. 

It  is  readily  exposed 

on  the  under  surface 

of  the  medulla  by  cut- 
ting   the    membrane, 

which  is  there  its  onlv 


^ 


Fig.  259.— 
Brain  of  Frog. 


covering  (Fig.  259). 


Fig.  260.  —  Nervous  System 
of  Frog. 


Frogs  and  toads  are  beneficial  (why  ? )  and  do  not  the  slight- 
est injury  to  any  interest  of  man.  If  toads  are  encouraged 
to  take  up  their  abode  in  a  garden,  they  will  aid  in  ridding 
it  of  insects.  A  house  may  be  made  in  a  shady  corner  with 
four  bricks,  or  better  still,  a  hole  a  foot  deep  may  be  dug  to 
furnish  them  protection  from 
the  heat  of  the  day.  A  toad's 
muzzle  is  not  so  tapering  as  a 
frog's  (why  ?),  its  feet  are  not 
so  fully  webbed  (why?),  and  its 
skin  is  not  so  smooth  (why  ?). 
Incase  of  doubt  open  the  mouth 
and  rub  the  finger  along  the  up- 
per jaw;  a  frog  has  sharp  teeth, 
a  toad  none  at  all.  The  tadpoles  of  frogs,  toads,  and  sala- 
manders are  much  alike.  In  toad's  spawn  the  eggs  lie  in 
strings  inclosed  in  jelly;  frogs  spawn  is  in  masses  (Fig.  248). 


^tv* 


tf^r"**- 


FIG.  261. —  Position  of  legs  in  tail- 
less (A)  and  tailed  {B)  amphibian. 


138 


ANIMAL   BIOLOGY 


Any  batrachian  may  easily  be  passed  around  the  class  after  placing 
it  in  a  tumbler  with  gauze  or  net  tied  over  top.  It  should  be  kept  in  a 
box  with  two  inches  of  moist  earth  on  the  bottom.  If  no  live  insects 
are  obtainable  for  feeding  a  toad,  bits  of  moist  meat  may  be  dangled 
from  the  end  of  a  string.  If  tadpoles  are  placed  in  a  pool  or  tub  in  a 
garden,  the  toads  hatched  will  soon  make  destructive  garden  insects 
become  a  rarity. 

Does  a  frog  or  a  salamander  have  the  more  primitive 
form  of  body  ?  Why  do  you  think  so  ?  Salamanders  are 
sometimes  called  mud  puppies.  The  absurd  belief  that 
salamanders  are  poisonous  is  to  be  classed  with  the  belief 
that  toads  cause  warts.  The  belief  among  the  ancients 
that  salamanders  ate  fire  arose  perhaps  from  seeing  them 
coming  away  from  fires  that  had  been  built  over  their 
holes  on  river  banks  by  travelers.  Their  moist  skin  pro- 
tected them  until  the  fire  became  very  hot. 

Describe  the  "mud  puppy"  shown  in  Fig.  262.  In  the 
West  the  pouched  gopher,  or  rat  (Fig.  371),  is  sometimes 
absurdly  called  a  salamander. 


FlG.  262.  —  Blind  Salamander  (Proteus  anguinus).    x  \.     Found  in  caves  and 
underground  streams  in  Balkans.     Gills  external,  tail  finlike,  legs  small. 


CHAPTER   XII 

REPTILfA  (REPTILES) 

This  class  is  divided  into  four  orders  which  have  such 
marked  differences  of  external  form  that  there  is  no  diffi- 
culty in  distinguishing  them.  These  orders  are  represented 
by  Lizards,  Snakes,  Turtles,  and  Alligators.  Of  these,  only 
the  forms  of  lizards  and  alligators  have  similar  propor- 
tions, .but  there  is  a  marked  difference  in  their  size, 
lizards  being,  in  general,  the  smallest,  and  alligators  the 
largest  of  the  reptiles. 

Comparison  of  Lizards  and  Salamanders.  — To  make  clear 
the  difference  between  reptiles  and  batrachians,  it  will  be 
well  to  compare  the  orders  in  the  two  classes  which  re- 
semble each  other  in  size  and  shape ;  namely,  lizards  and 


Fig.  263.  — A  Salamander.  Fig.  264.  — A  Lizard. 

salamanders  (Figs.  263  and  264).  State  in  a  tabular  form 
their  differences  in  skin,  toe,  manner  of  breathing,  develop- 
ment from  egg,  shape  of  tail,  habitat,  habits.  Each  has 
an  elongated  body,  two  pairs  of  limbs,  and  a  long  tail,  yet 
they  are  easily  distinguished.  Are  the  differences  sug- 
gested above  valid  for  the  other  batrachians  (frogs)  and 
other  reptiles  (eg.  turtles)?     Trace  the  same  differences 

139 


140 


ANIMAL   BIOLOGY 


between    the    toad    or  frog  (Fig.    250)  and   the    "horned 
toad,"  which  is  a  lizard  (Fig.   265), 

m 


Fig.  265.  — "Horned  Toad"  Lizard,  of  the  Southwest 
(Pluynosoma  cornita).   x'j. 


Study  of  a  Turtle  or  Tortoise 

Suggestions.  —  Because  of  the  ease  with  which  a  tortoise  or 
turtle  may  be  caught  and  their  movements  and  habits  studied,  it  is 
suggested  that  one  of  these  be  studied  as  an  example  of  reptiles. 
Besides  a  live  specimen,  a  skeleton  of  one  species  and  the  shells  of 
several  species  should  be  available. 

ttl 

la 


Fig.  266. —  European  Pond  Turtle  {Etnys  lutaria),    (After  Brehms.) 

The  body  (of  a  turtle  or  tortoise)  is  divided  distinctly  into 
regions  (Fig.  266).  Is  there  a  head  ?  Neck  ?  Trunk  ? 
Tail  ?     The  trunk  is  inclosed  by  the  so-called  shell,  which 


REP  T I  LI  A  141 

consists  of  an  upper  portion,  the  carapace,  and  a  lower 
portion,  the  plastron.  How  are  the  other  regions  covered  ? 
What  is  the  shape  of  the  head  ?  Is  the  mouth  at  the 
front,  or  on  the  under  side  ?  Where  are  the  nostrils  ? 
Are  the  motions  of  breathing  visible  ?  Is  there  a  beak  or 
snout  ?     Do  the  jaws  contain  teeth  ? 

Do  the  eyes  project?  Which  is  thinner  and  more 
movable,  the  upper  or  lower  lid  ?  Identify  the  third  eye- 
lid {nictitating  membrane).  It  is  translucent  and  comes 
from,  and  is  drawn  into,  the  inner  corner  of  the  eye.  It 
cleanses  the  eyeball.  Frogs  and  birds  have  a  similar 
membrane.  The  circular  ear  drum  is  in  a  depression  back 
of  the  angle  of  the  mouth.  What  other  animal  studied 
has  an  external  ear  drum  ? 

The  tortoise  has  a  longer,  more  flexible  neck  than  any 
other  reptile.  Why  does  it  have  the  greatest  need  for 
such  a  neck  ?  Is  the  skin  over  the  neck  tight  or  loose  ? 
Why  ? 

Do  the  legs  have  the  three  joints  or  parts  found  on  the 
limbs  of  most  vertebrates  ?  How  is  the  skin  of  the  legs 
covered?  Do  the  toes  have  claws?  Compare  the  front 
and  hind  feet.  Does  the  tortoise  slide  its  body  or  lift  it 
when  walking  on  hard  ground  ?  Lay  the  animal  on  its 
back  on  a  chair  or  table  at  one  side  of  the  room  in  view 
of  the  class.  Watch  its  attempts  to  right  itself.  Are 
the  motions  suited  to  accomplish  the  object  ?  Does  the 
tortoise  succeed  ? 

What  are  the  prevailing  colors  of  turtles  ?  How  does 
their  coloration  correspond  to  their  surroundings  ? 

What  parts  of  the  tortoise  extend  at  times  beyond  the 
shell  ?  Are  any  of  these  parts  visible  when  the  shell  is 
closed?  What  movements  of  the  shell  take  place  as  it  is 
closed  ?    Is  the  carapace  rigid  throughout  ?    Is  the  plastron  ? 


142 


ANIMAL   BIOLOGY 


The  Skeleton  (Fig.  267).  — The  carapace  is  covered  with 
thin  epidermal  plates  which  belong  to  the  skin.  The  bony 
nature  of  the  carapace  is 
seen  when  the  plates  are 
removed,  or  if  its  inner 
surface  is  viewed  (Fig. 
267).  It  is  seen  to  con- 
sist largely  of  wide  ribs 
(how  many  ?)  much  flat- 
tened and  grown  together 
at  their  edges.  The  ribs 
are  seen  to  be  rigidly  at- 
tached to  the  vertebrae. 
The  rear  projections  of 
the  vertebrae  are  flattened 
into  a  series  of  bony  plates 
which  take  the  place  of 
the  sharp  ridge  found 
along  the  backs  of  most 

vertebrates 


Fig.  267.  —  Skeleton  of  European 
Tortoise. 

C,rib  plates;  M,  marginal  plates;  B,  plastron; 
H,  humerus  bone;  R,  radius;  U,  ulna; 
Fe,  femur 


Fig.  268.  — Three-cham- 
bered Heart  of  a  Rep- 
tile (tortoise). 

a,  veins;  b,f,  right  and  left  auri- 
cles; eg,  ventricle ;  ii,  arteries  to 
lungs;  e,  veins  from  lungs;  i,  ft, 
two  branches  of  aorta.  Compare 
with  Fig  269  and  colored  Fig.  2. 


Show  that  the  shell 
of  a  turtle  is  not  homologous  with 
the  shells  of  mollusks.  Does  the 
turtle  have  shoulder  blades  and 
collar  bones  ?  Hip  bones  ?  Thigh 
bones  ?  Shin  bone  (fibia)  and  splint 
bone  (fibula)  ?     (Fig.  267.) 

Do  the  plates  formed  by  the  ribs 
extend  to  the  edge  of  the  cara- 
pace ?  See  Fig.  267.  About  how 
many  bony  plates  form  the  cara- 
pace ?  The  plastron  ?  Do  the 
horny  plates  outside  correspond 
to  the  bony  plates  of  the   shell  ? 


REPTILIA 


143 


Fig.  269. —  Plan  of  Rep- 
tilian Circulation. 
See  arrows. 


How  many  axial  plates  ?     How  many  costal  (rib)  plates  ? 

How    many    border    plates?     Which    plates    are  largest? 

Smallest  ?      Do   the    horny    plates 

overlap  like  shingles,  or  meet  edge 

to  edge  ?    Is  there  any  mark  where 

they    meet    on     the    bony    shell  ? 

Basing    it    upon     foregoing    facts, 

give  a  connected  and  complete  de- 
scription of    the   structure    of   the 

carapace.     Compare    the    skeleton 

of  the  turtle  with  that  of  the  snake, 

and    correlate    the    differences    in 

structure  with  differences  in  habits. 
Draw  the  tortoise  seen  from  the 

side  or  above,  with  its  shell  closed,  showing  the  arrange- 
ment of  the  plates. 

Place  soft  or  tender  vegetable 
food,  lettuce,  mushroom,  roots,  ber- 
ries, and  water,  also  meat,  in  reach 
of  the  turtle.  What  does  it  pre- 
fer? How  does  it  eat  ?  It  has  no 
lips  ;  how  does  it  drink  ? 

Study  the  movements  of  its  eye- 
balls and  eyelids,  and  the  respira- 
tory and  other  movements  already 
mentioned.  State  a  reason  for 
thinking  that  no  species  of  land 
animals  exists  that  lacks  the  sim- 
ple power  of  righting  itself  when 

turned  on  its  back. 
Fig.  270.  — Reptilian  Vis- 

cera  (lizard).  Tortoise,  Turtle,  Terrapin.  — The 

ir,  windpipe;  h, heart;  hi,  lungs;      turtles  belong  to  the  order  of  rep- 

lr,   liver;    ma,   stomach;    dd,  11      1  7     7        •  ,, 

md,  intestines;  £,$,  bladder.         tiles    called    chelonians.     No    one 


144  ANIMAL   BIOLOGY 

can  have  any  difficulty  in  knowing  a  member  of  this  order. 
The  subdivision  of  the  order  into  families  is  not  so  easy, 
however,  and  the  popular  attempts  to  classify  chelonians 
as  turtles,  tortoises,  and  terrapins  have  not  been  entirely 
successful.  Species  with  a  vaulted  shell  and  imperfectly 
webbed  toes  and  strictly  terrestrial  habits  are  called  tor- 
toises. Species  with  flattened  shells  and  strictly  aquatic 
habits  should  be  called  terrapins  {e.g.  mud  terrapin).  They 
have  three  instead  of  two  joints  in  the  middle  toe  of  each 
foot.  The  term  turtle  may  be  applied  to  species  which  are 
partly  terrestrial  and  partly  aquatic  {e.g.  snapping  turtle 
(Fig.  271)).     Usage,  however,  is  by  no  means  uniform. 


Fig.  271.  — Snapping  Turtle  (Ckefydra  serpentina). 

Most  reptiles  eat  animal  food ;  green  terrapins  and  some 
land  tortoises  eat  vegetable  food.  Would  you  judge  that 
carnivorous  chelonians  catch  very  active  prey  ? 

The  fierce  snapping  turtle,  found  in  ponds  and  streams, 
sometimes  has  a  body  three  feet  long.  Its  head  and  tail 
are  very  large  and  cannot  be  withdrawn  into  the  shell. 
It  is  carnivorous  and  has  great  strength  of  jaw.  It  has 
been  known  to  snap  a  large  stick  in  two.  The  box  tortoise 
is  yellowish  brown  with  blotches  of  yellow,  and  like  its 
close  kinsman,  the  pond  turtle  of  Europe  (Fig.  266),  with- 
draws itself  and  closes  its  shell  completely.  Both  lids  of  the 
plastron  are  movable,  a  peculiarity  belonging  to  these  two 
species.     The  giant  tortoise  of  the  Galapagos  Islands,  ac- 


REP  TIL  I  A 


145 


cording  to  Lyddeker,  can  trot  cheerfully  along  with  three 
full-grown  men  on  its  back.  "Tortoise  shell"  used  for 
combs  and  other  articles  is  obtained  from  the  overlapping 
scales  of  the  hawkbill  turtle,  common  in  the  West  Indies. 
The  diamond-back  terrapin,  found  along  the  Atlantic  Coast 
from  Massachusetts  to  Texas,  is  prized  for  making  soup. 


' 


^Plfe;. 


Fig.  272.  —  A  Rattlesnake. 

Poisonous  snakes  of  United 
States  named  in  order  of  virulence  : 
1.  Coral  snakes,  Elaps,  about  sev- 
enteen red  bands  bordered  with  yel- 
low and  black  (colored  figure  6) 
(fatal).  2.  Rattlesnakes  (seldom 
fatal).  3.  Copperhead  (may  kill 
a     small     animal     size     of     dog). 

4.  Water  moccasin  (never  fatal). 

5.  Ground  rattler.  —  Effects:  Pulse 
fast,  breathing  slow,  blood  tubes 
dilated,  blood  becomes  stored  in  ab- 
dominal blood  tubes,  stupefaction 


Fig.  273(7.— Head  of 
Viper,  showing  typical 
triangular  shape  of  head 
of  venomous  snake. 


Fig.  273  b. —  Side  View, 
showing  poison  fangs  ;  also 
tongue  (forked,  harmless). 


Fig.  274.  —  Viper's  Head, 
showing  poison  sac  at 
base  of  fangs. 


Fig.  275.  — Skull,  showing 
teeth,  fangs,  and  quadrate 
bone  to  which  lower  jaw 
is  joined.     See  Fig.  284. 


146 


ANIMAL   BIOLOGY 


Fig.  276.  —  "  Glass  Snake,"  a  lizard 
without  legs. 


and  death  from  blood  being  withdrawn  from  brain.  Al 
ways  two  punctures,  the  closer  together  the  smaller  the 
snake.  Remedies;  Ligature  between  wound  and  heart, 
lance  wound  and  suck  ;  inject  into  wound  three  drops  of  1 
per  cent  solution  of  chromic  acid  or  potassium  perman- 
ganate. Give  strychnine,  hypodermically,  until  strychnine 
symptoms  (twitchings)  appear.  If  symptoms  of  collapse 
recur,  repeat  dose.  Digitalin  or  caffein  acts  like  strych- 
nine ;  alcohol  has  opposite  effect. 

Protective  Coloration  and  Mimicry.  —  When  an  animal 
imitates  the  color  or  form  of  its  inanimate  surroundings  it 

is  said  to  be  protectively  col- 
ored or  formed.  Give  an 
instance  of  protective  col- 
oration or  form  among 
lizards;  butterflies;  grass- 
hoppers; amphibians;  echi- 
noderms.  When  an  animal  imitates  the  color  or  form  of 
another  animal  it  is  said  to  mimic  the  animal.  Mimicry 
usually  enables  an  animal  to  deceive 
enemies  into  mistaking  it  for  an  ani- 
mal which  for  some  reason  they  avoid. 
The  milkweed  butterfly  has  a  taste 
that  is  repulsive  to  birds.  The  vice- 
roy butterfly  is  palatable  to  birds,  but 
it  is  left  untouched  because  of  its 
close  resemblance  to  the  repulsive 
milkweed  butterfly.  The  harlequin 
snake  {E laps')  of  the  Gulf  states  is  the 
only  deadly  snake  of  North  America 
(Figs.  277,  278).  It  is  very  strikingly  colored  with  rings  of 
scarlet,  yellow,  and  black.  This  is  an  example  of  warning 
coloration.     The  coral  snake  {Lampropeltis)  has  bands  of 


Fig.  277. —  Skull  of 

Elaps.  See  colored 

Fig-  5- 


Fig.  278.  =  Skull  of 
Lampropeltis. 


CoLORi-.n  Figures  i,  2.  3.  —  Circulation  in  Fish,  Reptile,  Mammal. 

In  which  is  blood  from  heart  all  impure  ?     Mixed  ?     Both  pure  and  impure  ? 


Fig.  4.  —  ANATOMY  of  Cakp.     For  description  see  Fig.  220,  page  117. 


Fig.  5  —  Harlequin  Snake  \l 


The  Harmless 

Cora  1.  Snake 

mimics  the 

Deadly  Harlequin 

Snake. 


Kig.  6.  —  Coral  Snake  (Lampropeltis). 


OF  THE 

DIVERSITY 

OF 


REPTILIA 


147 


scarlet,  yellow,  and  black  (colored  Fig.  6)  of  the  same  tints, 
and  it  is  hardly  distinguishable  from  the  harlequin.       The 


'Vfec'^SSVtN, 


FIG.  279.  —  Gila  Monster  (Heloderma  suspectuin),  of  Arizona.  Ifpoisonous.it 
is  the  only  instance  among  lizards.  It  is  heavy-built,  orange  and  black  mottled, 
and  about  16  inches  long.     Compare  it  with  the  green  lizard  (Fig.  280). 


coral  snake  is  said  to  mimic  the  harlequin  snake 
imitates  the  quiet  inoffensive  hab- 
its of  the  harlequin  snake,  which 
fortunately  does  not  strike  except 
under  the  greatest  provocation. 
The  rattles  of  the  less  poisonous 
and  seldom  fatal  rattlesnake 
(Fig.  272)  may  be  classed  as  an 
example  of  warning  sound  which 
most  animals  are  quick  to  heed 
and  thus  avoid  encounters  which 
might  be  destructive  to  either  the 
snake  or  its  enemy. 

Survival  of  the  Fittest.  —  The  two 
facts  of  most  far-reaching  importance 
in  the  history  of  animals  and  plants 
are  :  ( 1 )  Heredity  ;  animals  inherit 
the  characteristics  of  their  parents. 
(2)  Variation ;  animals  are  not  ex- 
actly like  their  parents.  The  first 
fact  gives  stability,  the  second  makes 


It  also 


Fig.  280.  —  Chameleon  {Ano- 
lis),  or  green  lizard  of  south- 
ern U.S.  Far  excels  European 
chameleon  (Fig.  281)  and  all 
known  animals  in  power  of 
changing  color  (green,  gray, 
yellow,  bronze,  and  black). 


148 


ANIMAL   BIOLOGY 


Fig.  281.  —  Chameleon  of  Southern  Europe. 


progress  or  evolution  possible.  The  climate  of  the  world  is  slowly 
changing,  and  animals  must  change  to  adapt  themselves  to  it.  A 
more  sudden  change  of  environment  (surroundings)  of  animals 
occurs  because  of  migration  or  isolation  ;  these  in  turn  are  caused 

by  the  crowding  of 
other  animals  or  by 
the  formation  or  dis- 
appearance of  geo- 
graphical barriers, 
such  as  deserts,  water, 
mountain  chains. 

The  young  vary  in 
many  ways  from  their 
parents.  Some  have 
a  more  protective  color 
or  form,  sharper  claws, 
swifter  movements,  etc.  The  individuals  possessing  such  bene- 
ficial variations  live  longer  and  leave  more  offspring,  and  because 
of  heredity  transmit  the  desirable  qualities  to 
some  of  their  young.  Variations  which  are  dis- 
advantageous for  getting  food,  defense,  etc.,  cause 
shorter  life  and  fewer  offspring.  Thus  the  fittest 
survive,  the  unfit  perish  ;  an  automatic  natural 
selection  occurs. 

Darwin  taught  that  variations  are  infinitesimal 
and  gradual.  Recent  experiments  and  observa- 
tions seem  to  show  that  many  variations  are  by 
sudden  jumps,  somewhat  resembling  so-called 
"  freaks  of  nature."  As  to  whether  these  "  sports," 
or  individuals  with  new  peculiarities,  survive, 
depends  upon  their  fitness  for  their  environ- 
ment. "Survival  of  the  fittest "  results  from  this 
natural  selection,  but  the  selection  occurs  be- 
tween animals  of  marked,  not  infinitesimal,  dif- 
ferences, as  Darwin  taught.  Darwin's  theory  is 
probably  true  for  species  in  the  usual  state  of  nature  ;  the  new 
theory  (of  De  Vries)  is  probably  true  for  animals  and  plants  under 
domestication  and  during  rapid  geographical  changes. 


Fig.  282.  —  Em- 
bryo of  A 
Turtle,  show- 
ing four  gill  slits. 
(Challenger  Re- 
port.) 


REP  TILIA 


149 


Table  for  Review  (for  notebooks  or  blackboards). 


Fish 

Tadpole 

Frog 

Turtle 

Lizard 

Limbs,  kind  and 
number 

Are  claws  present  ? 
How  many  ? 

Covering  of  body 

Teeth,    kind    of,     if 
present 

Which   bones    found 
in  man  are  lacking? 

Chambers  of  heart 

Respiration 

Movements 

FIG.  283.  —  Big-headed  Turtle  (Platysternum  megcdocephaluin).  x  \.  China. 
This  and  Fig.  282  suggest  descent  of  turtles  from  a  lizardlike  form.  Figure  282 
shows  earlier  ancestors  to  have  been  gill  breathers. 


CHAPTER  XIII 

BIRDS 

Suggestions.  —  The  domestic  pigeon,  uV  fowl,  and  the  English 
sparrow  are  most  commonly  within  the  rf-ich  of  students.  The 
last  bird  has  become  a  pest  and  is  almost  the  only  bird  whose 
destruction  is  desirable.  The  female  is  somewhat  uniformly  mot- 
tled with  gray  and  brown  in  fine  markings.  The  male  has  a  black 
throat  with  the  other  markings  of  black,  brown,  and  white,  in 
stronger  contrast  than  the  marking  of  the  female.  As  the  different 
species  of  birds  are  essentially  alike  in  structural  features,  the  direc- 
tions and  questions  may  be  used  with  any  bird  at  hand.  When 
studying  featners,  one  or  more  should  be  provided  for  each  pupil 
in  the  class.     The  feet  and  bills  of  birds  should  be  kept  for  study. 

\  Does  the  body  of  the  bird,  like  the  toad  and  turtle,  have 
a  head,  trunk,  tail,  and  two  pairs 
of  limbs  ?  Do  the  fore  and  hind 
limbs  differ  from  each  other  more  or 
less  than  the  limbs  of  other  backboned 
animals  ?  Does  any  other  vertebrate  use 
purposes  as  widely  different  ? 
^,  Does  the  eyeball  have  parts  corresponding 
to  the  eyeball  of  a  fish  or  frog;  viz.,  cornea,  iris,  pupil? 
Which  is  more  movable,  the  upper  or  lower  eyelid '?  Are 
there  any  lashes?  The  bird  (like  what  other  animal?)  has 
a  third  eyelid,  or  nictitating  membrane.  Compare  its 
thickness  with  that  of  the  other  lids.  Is  it  drawn  over 
the  eyeball  from  the  inner  or  outer  corner  of  the  eye  ? 
Can  you  see  in  the  human  eye  any  wrinkle  or  growth 
which  might  be  regarded  as  remains,  or  vestige,  of  such  a 
membrane  ? 

150 


BIRDS 


151 


How  many  nostrils  ?  In  which  mandible  are  they 
located  ?  Are  they  nearer  the  tip  or  the  base  of  the 
mandible  ?  (Fig.  284.)  What  is  their  shape  ?  Do  the  nasal 
passages  go  directly  down  through  the  mandible  or  do  they 
go  backwaid?  Is  the  inner  nasal  opening  into  the  mouth 
or  into  the  throat  ? 

The  beat  or  bill  consists  of  the  upper  and  lower  man- 
dibles. The  outside  of  the  beak  seems  to  be  of  what  kind 
of  material  ?  Examine  the  decapitated  head  of  a  fowl  or  of 
a  dissected  bird,  and  find 
if  there  is  a  covering  on 
the  bill  which  can  be  cut 
or  scrapea  off.  Is  the 
mass  of  the  biU  of  bony 
or  horny  matern  ) .'  With 
what  part  of  the  human 
head  are  the  mandibles 
homologous?  (Fig  284.) 

Ears.  —  Do  birds  b  ave 
external  ears  ?  Is  tnere  an  external  opening  leading  to  the 
ear?  In  searching  fcr  it,  blow  or  push  forward  the  feath- 
ers. If  found,  notice  its  location,  size,  shape,  and  what 
surrounds  the  opening.  There  is  an  owl  spoken  of  as  the 
long-eared  owl.     Are  its  ears  long  ? 

The  leg  has  three  divisions :  the  uppermost  is  the  thigh 
(called  the  "second  joint"  in  a  fowl);  the  middle  division 
is  the  sJiank  (or  "drumstick");  and  he  lowest,  vhich  is 
the  slender  bone  covered  with  scales ,  is  formed  by  the 
union  of  the  ankle  and  instep.  (The  bones  of  the  three 
divisions  are  named  the  femur,  tibiotarsus,  and  tarsometa- 
tarsus).  The  foot  consists  entirely  of  toes,  the  bones  of 
which  are  called  phalanges.  Is  there  a  bone  in  each  claw  ? 
(See  Fig.  285.)     Supply    the   numerals  in  this  sentence: 


Fig.  284.  — Skull  of  Domestic  Fowl. 

q,  quadrate  ("  four-sided  ")  bone  by  which  lower 
jaw  is  attached  to  skull  (wanting  in  beasts,  pres- 
ent in  reptiles  ;  see  Fig.  277). 


152 


ANIMAL  BIOLOGY 


toes,  the 
-  joints  ; 


The  pigeon  has  - 
hind  toe  having 
of  the   three   front   toes,    the 

inner   has  joints   (count 

the    claw   as  one   joint),   the 


Fig.  286.  —  Skeleton  of  Bird. 


Rh,  vertebrae;   CI,  clavicle;   Co,  coracoid;   Sc,  scap- 
ula;   St,  sternum;    H,  humerus;     R,  radius;     U, 
ulna;  P,  thumb;  Fe,  femur;  T,  tibia.    See  Fig.  394. 
Questions  :    Which  is  the  stiflfest   portion   of  the 
vertebral  column  ?     How  are  the  ribs  braced  against 
each   other  ?     Which   is  longer,  thigh  bone  or  shin  ? 
Compare  shoulder  blade  with  man's  (Fig.  399).  Which 
is  the  extra  shoulder  bone  ?     Compare  tail  vertebras 
with  those  of  extinct  bird,  Fig.  290. 


Fig.  285.  — Leg  Bones 
of  Bird. 

middle    has    

joints,     and      the 

outer  toe  has 

joints   (Fig.   285). 
Is  the  thigh  of  a  bird  bare  or 
feathered  ?     The  shin  ?     The 
ankle  ?     Where  is  the  ankle 
joint  of    a   bird  ?     Do 
you    see    the    remains 
of   another    bone   (the 
splint  bone,   or  fibula) 
on    the    shin    bone    of 
the  shank?     (Fig.  285 
or  286.)     Why  would 
several    joints    in    the 
ankle  be    a    disadvan- 
tage to  a  bird  ? 


BIRDS 


153 


The  thigh  hardly  projects  beyond  the  skin  of  the  trunk, 
as  may  be  noticed  in  a  plucked  fowl.  The  thigh  extends 
forward  from  the  hip  joint  (Figs.  286,  299)  in  order  to  bring 
the  point  of  support  forward  under  the  center  of  weight. 
Why  are  long  front  toes  more  necessary  than  long  hind  toes  ? 
As  the  bird  must  often  bring  its  head  to  the  ground,  the 
hip  joints  are  near  the  dorsal  surface  and  the  body  swings 
between  the  two  points  of  support  somewhat  like  a  silver 
ice  pitcher  on  its  two  pivots.  Hence  stooping,  which  makes 
a  man  so  unsteady,  does  not  cause  a  bird  to  lose  steadiness. 

The  wing  has  three  divisions  which  correspond  to  the 
upper  arm,  forearm,  and  hand  of  man  (Fig.  286).  When 
the  wing  is  folded,  the  three  divisions  lie  close  alongside 
each  other.  Fold  your  arm  in  the  same  manner.  The 
similarity  of  the  bones  of  the  -first  and  second  divisions  to 
the  bones  of  our  upper  arm  and  forearm  is  very  obvious 
(Fig.  286).  Ex- 
plain. The  hand  of 
a  bird  is  furnished 
with  only  three  dig- 
its (Fig.  287).  The 
three  palm  bones 
(metacarpals)  are 
firmly  united  (Fig. 
287).  This  gives 
firmness  to  the 
stroke  in  flying. 

That  the  bird  is 
descended  from  ani- 
vials  which  had  the 
fingers  and  palm  bones  less  firmly  united  is  shown  by 
comparing  the  hands  of  a  chick  and  of  an  adult  fowl 
(Figs.  287,  288).     The  wrist  also  solidifies  with  age,  the 


DG.2       PQ.3 

Fig.  287.  —  Hand  and  Wrist  of  Fowl 
(after  Parker). 

DG.  1-3,  digits:  MC.  1-3,  metacarpals; 
CC,  3,  wrist. 


Fig.  288.  — Hand,  Wrist  (c),  Forearm,  and 
Elbow  of  Young  Chick  (after  Parker). 


154 


ANIMAL    BIOLOGY 


Fig.  289.  —  Breast- 
bone and  Shoul- 
der Bones  of 
Cassowary. 


five  carpals  of  the  chick  being  reduced  to  two  in  the  fowl 
(Figs.  287,  288).  The  thumb  or  first  digit  has  a  separate 
covering  of  skin  from  the  other  digits,  as 
may  be  seen  in  a  plucked  bird.  The  de- 
generate hand  of  the  fowl  is  of  course 
useless  as  a  hand  (what  serves  in  its 
place  ?)  but  is  well  fitted  for  firm  support 
of  the  feathers  in  flying.  The  two  bones 
of  the  forearm  are  also  firmly  joined. 
There  are  eighteen  movable  joints  in  our 
arm  and  hand ;  the  bird  has  only  the  three 
joints  which  enable  it  to  fold  its  wing. 
The  wrist  joint  is  the  joint  in  the  forward  angle  of  the  wing. 

Since  the  fore  limbs  are  taken  up  with  loco- 
motion, the  grasping  function  has  been  as- 

otIw 
sumed  by  the  jaws.    How  does  their  ~.t*$'U. 

shape  adapt  them  to  this  use?     For 
the  same  reason  the  neck  of  a  bird 
surpasses  the  necks  of  all  other  ani- 
mals in  what  respect?     Is  the  trunk 
of   a   bird 
flexible  or 
inflexible  ? 
There     is 
thus  a  cor- 
relation between   struc- 
ture of  neck  and  trunk. 
Explain.        The     same 
correlation  is  found  in 

which   of   the   reptiles  ?     ,-,  ,  „  ,     , 

1  Fig.   290.  —  A   Fossil  Bird   {archtsopteryx) 

(Why     does    rigidity     of  found  in  the  rocks  of  a  former  geological 

trunk  require  flexibility        epo°  ' 

Question:    Find  two  resemblances  to  reptiles  in 
Ot     neCK.  f  )         Why     dOeS        this  extinct  bird  absent  from  skeletons  of  extant  birds. 


BIRDS 


155 


the  length  of  neck  in  birds  correlate  with  the  length  of 
legs?  Examples?  (See  Figs.  314,  315,  332.)  Exceptions? 
(Fig.  324.)  Why  does  a  swan  or  a  goose  have  a  long 
neck,  though  its  legs  are  short  ? 

To  make  a  firm  support  for  the  wings  the  vertebrae  of 
the  back  are  immovably  joined,  also  there  are  three  bones 
in  each  shoulder,  the  collar  bone, 
the  shoulder  blade,  and  the 
coracoid  bone  (Fig.  286).  The 
collar  bones  are  united  (why  ?) 
and  form  the  "  wishbone  "  or 
"  pulling  bone."  To  furnish  sur- 
face for  the  attachment  of  the 
large  flying  muscles  there  is  a 
prominent  ridge  or  keel  on  the 
breastbone  (Fig.  286).  It  is 
lacking  in  most  birds  which  do 
not  fly  (Fig.  289). 

The  feathers  are  perhaps  the 
most  characteristic  feature  of 
birds.  The  large  feathers  of  the 
wings  and  tail  are  called  quill 
feathers.  A  quill  feather  (Fig. 
291)  is  seen  to  consist  of  two 
parts,  the  shaft,  or  supporting 
axis,  and  the  broad  vane  or  web. 
What  part  of  the  shaft  is  round  ?  Hollow  ?  Solid  ?  Is 
the  shaft  straight  ?  Are  the  sides  of  the  vane  usually 
equal  in  width  ?  Can  you  tell  by  looking  at  a  quill  whether 
it  belongs  to  the  wing  or  tail,  and  which  wing  or  which 
side  of  the  tail  it  comes  from  ?  Do  the  quills  overlap 
with  the  wide  side  of  the  vane  above  or  beneath  the  next 
feather  ?    Can  you  cause  two  parts  of  the  vane  to  unite  again 


Fig.  291.  —  Quill  Feather. 

D,  downy  portion. 


1 56 


.lXf.UA/.    BIOLOGY 


by  pressing  together  the  two  sides  of  a  split  in  the 'vane  ? 
Does  the  web  separate  at  the  same  place  when  pulled  until 

h         it  splits  again  ? 

The  hollow  part  of  the 
shaft  of  a  quill  feather  is 
called  the  quill.  The  part 
of  the  shaft  bearing  the 
vane  is  called  the  racliis 
(ra-kis).  The  vane  consists 
of  slender  barbs  which  are 
branches  of  the  shaft  (II, 
Fig.  292).  As  the  name 
indicates  (see  dictionary),  a 
barb  resembles  a  hair.  The 
barbs  in  turn  bear  second- 
ary branches  called  bar- 
bales,  and  these  again  have 
shorter  branches  called  bar- 
bicels  (III,  Fig.  292).  These  are  sometimes  bent  in  the 
form  of  hooklets  (Fig.  292,  III),  and  the  hooklets  of 
neighboring  barbules  interlock,  giv- 
ing firmness  to  the  vane.  When  two 
barbules  are  split  apart,  and  then  re- 
united by  stroking  the  vane  between 
the  thumb  and  finger,  the  union  may 
be  so  strong  that  a  pull  upon  the  vane 
will  cause  it  to  split  in  a  new  place 
next  time. 

There   are  four  kinds  of    feathers, 

(1)  the  quill  feathers,  just  studied; 

(2)  the  contour  feathers  (I,  Fig.  292), 
which  form  the  general  surface  of  the  body  and  give  it  its 
outlines;  (3)  the  dotvny  feathers  (Fig.  293),  abundant  on 


Fig.  292— I,  Contour  Feather. 

II,  III,  Parts  of  Quill  Feather, 

enlarged. 


Fig.  293.  —  A  Down 
Feather,  enlarged. 


BIRDS 


157 


nestlings  and  found  among  the  contour  feathers  of  the 
adult  but  not  showing  on  the  surface  ;  (4)  the  pin  feathers, 
which  are  hair-like,  and  which  are  removed  from  a  plucked 
bird  by  singeing.  The  contour  feathers  are  similar  in 
structure  to  the  quill  feathers.  They  protect  the  body 
from  blows,  overlap  so  as  to  shed  the  rain,  and,  with  the 
aid  of  the  downy  feathers  retain  the  heat,  thus  accounting 
for  the  high  temperature  of  the  bird.  The  downy  feathers 
are  soft  and  fluffy,  as  they  possess  few  or  no  barbicels ; 
sometimes  they  lack  the  rachis  (Fig.  293).  The  pin  feath- 
ers are  delicate  horny  shafts,  greatly  resembling  hairs,  but 
they  may  have  a  tuft  of  barbs  at  the  ends. 

A  feather  grows  from  a  small  projection  (or  papilla)  found 
at  the  bottom  of  a  depression  of  the  skin.  The  quill  is 
formed  by  being  molded  around  the  papilla.  Do  you  see 
any  opening  at  the  tip  of  the  quill  for  blood  vessels  to  enter 
and  nourish  the  feather  ?  What  is  in  the  quill  ?  (Fig.  291.) 
The  rachis  ?  A  young  con- 
tour or  quill  feather  is  in- 
closed in  a  delicate  sheath 
which  is  cast  off  when  the 
feather  has  been  formed. 
Have  you  seen  the  sheath 
incasing  a  young  feather  in 
a  molting  bird  ? 

There  are  considerable 
areas  or  tracts  on  a  bird's 
skin  without  contour  feath- 
ers. Such  bare  tracts  are 
found  along  the  ridge  of  the  breast  and  on  the  sides  of 
the  neck.  However,  the  contour  feathers  lie  so  as  to  over- 
lap and  cover  the  whole  body  perfectly  (Fig.  294). 

The  shedding  of  the  feathers  is  called  molting.    Feathers, 


Fig.  294.  — Dorsal  and  Ventral 
View  of  Plucked  Bird,  showing 
regions  where  feathers  grow. 


i58 


ANIMAL  BIO  LOG  Y 


like  the  leaves  of  trees,   are    delicate  structures   and  lose 
perfect  condition   with   age.     Hence  the    annual  renewal 

of  the  feathers  is 
an  advantage.  Most 
birds  shed  twice  a 
year,  and  with  many 
the  summer  plum- 
age is  brighter  col- 
ored than  the  winter 
plumage.  When  a 
feather  is  shed  on 
one  side,  the  corre- 
sponding feather  on 
the     other     side     is 

always   shed   with  it.     (What   need  for   this  ?)      A  large 

oil  gland  is  easily  found  on  the 

dorsal  side  of  the  tail.    How  does 

the    bird    apply    the    oil    to    the 

feathers  ? 


Fig.  295.  — Wing  of  Bird. 

/,  false  quills  (on  thumb) ;  2,  primaries;  3>  secondaries; 
tertianes  Jdark)  are  one  above  another  at  right; 
a,  b,  coverts. 


A 

Fig.  296. 

A,  point  dividing  primaries  from  second- 
aries; B,  coverts. 

In  describing  and  classifying 
birds,  it  is  necessary  to  know  the 
names  of  the  various  external 
regions  of  the  body  and  plum- 
age. These  may  be  learned  by 
studying  Figs.  295,  296,  297,  298, 


Fig.  297.  — Cedar  Waxwing, 
with  regions  of  body  marked. 
S,  forehead;  Sc,  crown  (with  crest); 
Hh,  nape;  A",  throat;  Br,  breast; 
Ba,  lower  parts;  A,  back;  AY,  tail; 
B,  tail  coverts;  P,  shoulder  feathers 
(scapulars)  ;  T,  wing  coverts;  HS, 
primaries;  AS,  secondaries;  Al, 
thumb  feathers. 

The  quills  on  the  hand 


BIRDS 


159 


N^ 


are  called  primaries,  those  on  the  forearm  are  the  sec- 
ondaries, those  on  the  upper  arm  are  the  tertiaries.  Those 
on  the  tail  are  called  the  tail  quills.  The  feathers  at  the 
base  of  the  quills  are  called  the  coverts.  The  thumb  bears 
one  or  more  quills  called  the  spurious  quills.  Is  the  wing 
concave  on  the  lower  or  upper 
side  ?  What  advantage  is  this 
when  the  bird  is  at  rest  ?  When 
it  is  flying  ? 

Control  of  Flight.  —  Did  you  ever 
see  a  bird  sitting  on  a  swinging 
limb  ?  What  was  its  chief  means 
of  balancing  itself  ?  When  flying, 
what  does  a  bird  do  to  direct  its 
course  upward  ?  Downward  ?  Is 
the  body  level  when  it  turns  to 
either  side  ?  Birds  with  long, 
pointed  wings  excel  in  what  respect  ?  Examples  ?  Birds 
with  great  wing  surface  excel  in  what  kind  of  flight  ?  Ex- 
amples. Name  a  common  bird  with  short  wings  which 
has  a  labored,  whirring  flight.  Is  its  tail  large  or  small  ? 
Does  it  avoid  obstacles  and  direct  its 
flight  well  ?  Why  or  why  not?  When 
a  boat  is  to  be  turned  to  the  right, 
must  the  rudder  be  pulled  to  the  right 
or  the  left  ?  (The  rudder  drags  in 
the  water  and  thus  pulls  the  boat 
around.)     When  the  bird   wishes  to 

Fig.  299.  — position  of     go  upward,  must  its  tail  be  turned  up 
Limbs  of  Pigeon.  .  .      TT  .         ... 

or  down  ?     How  when  it  wishes  to  go 

down  ?     When  a  buzzard  soars  for  an  hour  without  flapping 

its  wings,  does  it  move  at  a  uniform  rate  ?     For  what  does 

it  use  the  momentum  gained  when  scoing  with  the  wind  ? 


Fig.  298.  —  Plan  of  Bird. 

s,  center  of  gravity. 


i6o 


ANIMAL   BIOLOGV 


Flying.  —  When  studying  the  quill  feathers  of  the  wing, 
you  saw  that  the  wider  side  of  the  vane  is  beneath  the 
feather  next  behind  it.  During  the  downward  stroke  of 
the  wing  this  side  of  the  vane  is  pressed  by  the  air  against 


Fig.  300. 

a,  clambering  foot  of  chimney  sweep;  i,  climbing  foot  of  woodpecker;  c,  perching  foot  of 
thrush;  d,  seizing  foot  of  hawk;  e,  scratching  foot  of  pheasant;  /,  stalking  foot  of  king- 
fisher; g,  running  foot  of  ostrich;  h,  wading  foot  of  heron;  i,  paddling  foot  of  gull; 
k,  swimming  foot  of  duck;  /,  steering  foot  of  cormorant;  m,  diving  foot  of  grebe;  »,  skim- 
ming foot  of  coot.     Question:   Does  any  bird  use  its  foot  as  a  hand?     (,Fig.  320.) 

the  feather  above  it  and  the  air  cannot  pass  through  the 
wing.  As  the  wing  is  raised  the  vanes  separate  and 
the  air  passes  through.  The  convex  upper  surface  of 
the  wing  also  prevents  the  wing  from  catching  air  as 
it  is   raised.      Spread  a  wing  and  blow    strongly    against 


BIRDS 


161 


its  lower  surface ;    its   upper  surface.     What  effects   are 
noticed  ? 

Study  the  scales  on  the  leg  of  a  bird  (Fig.  300).  Why  is 
the  leg  scaly  rather  than  feathered  from  the  ankle  down- 
ward ?  Which  scales  are  largest?  (Fig.  300.)  How  do 
the  scales  on  the  front  and  back  differ  ?  What  can  you 
say  of  the  scales  at  the  bottom  of  the  foot ;  at  the  joints 
of  the  toes  ?  Explain.  How  does  the  covering  of  the 
nails  and  bill  compare  in  color,  texture,  hardness  and  firm- 
ness of  attachment  with  the  scales  of  the  leg  ? 

Draw  an  outline  of  the  bird  seen  from  the  side.      Make 
drawings  of   the  head  and   feet 
more    detailed   and  on  a  larger 
scale. 

Why  does  a  goose  have  more 
feathers  suitable  for  making  pil- 
lows than  a  fowl  ?  In  what 
country  did  the  domestic  fowl 
originate?  (Encyclopedia.)  Why 
does  a  cock  crow  for  day  ? 
(Consider  animal  life  in  jungle.) 

Activities  of  a  Bird.  —  Observe 
a  bird  eating.  Does  it  seem  to 
chew  or  break  its  food  before 
swallowing  ?  Does  it  have  to 
lift  its  head  in  order  to  swallow 
food  ?  To  swallow  drink  ?  Why 
is  there  a  difference  ?  After  feed- 
ing the  bird,  can  you  feel  the 
food  in  the  crop,  or  enlargement 
of  the  gullet  at  the  base  of  the 
neck  ?     (Fig.  304.) 

Feel  and  look  for  any  move- 
in 


Fig.  301.  — An  Altrical  Bird, 
i.e.  poorly  developed  at  hatch- 
ing. Young  pigeon,  naked, 
beak  too  weak  for  eating. 


Fin.  302.  —  A  Precocial  Bird 
(well  developed  at  hatching). 
Feathered,  able  to  run  and  to 
pick  up  food.  Precocity  is  a 
sign  of  instinctive  life  and  low 
intelligence.  A  baby  is  not  pre- 
cocious. 

Question:  Is  pigeon  or  fowl  ex- 
posed to  more  dangers  in  infancy  ? 


l62 


ANIMAL  BIOLOGY 


ments  in  breathing.  Can  you  find  how  often  it  breathes 
per  minute  ?  Place  hand  under  the  bird's  wing.  What 
do  you  think  of  its  temperature ;  or  better,  what  tempera- 
ture is  shown  by  a  thermometer  held  under  its  wing  ?  Do 
you  see  any  connection  between  the  breathing  rate  and  the 
temperature?  Test  (as  with  the  crayfish)  whether  a  bird 
can  see  behind  its  head  ?  Notice  the  movements  of  the 
nictitating  membrane.     Does  it  appear  to  be  transparent  ? 

Watch  a  bird  fly  around  a  closed  room  and  review  the 
questions  on  Control  of  Flight. 

Bend  a  bird's  leg  and  see  if  it  has  any  effect  upon  its 
toes.  Notice  a  bird  (especially  a  large  fowl)  walk  to  see 
if  it  bends  its  toes  as  the  foot  is  lifted.  Pull  the  rear 
tendon  in  a  foot  cut  from  a  fowl  for  the  kitchen.  Does 
the  bird  have  to  use  muscular  exertion  to  grasp  a  stick 
upon  which  it  sits  ?  Why,  or  why  not  ?  When  is  this 
bending  of  the  toes  by  bending  the  legs  of  special  ad- 
vantage to  a  hawk  ?  To  a  duck  ?  A  wading  bird  ?  Why 
is  a  fowl  safe  from  a  hawk  if  it  stands  close  to  a  tree  ? 

Do  you  see  any  signs  of  teeth  in  the  bird's  jaws  ?     Why 

are    duck's    "  teeth  "    (so    called  by  children)  not   teeth  ? 

,f  Can  the  tongue  of  a  bird  be 

a 

pulled  forward  ?  (Fig.  303.) 
What  is  its  shape  ?  If  there 
is  opportunity,  dissect  and 
study  the  slender,  bony 
(hyoid)  apparatus  to  which 
the  base  of  the  tongue  is 
attached  (Fig.  303),  the  open- 
ing of  the  windpipe,  or 
trachea,  the  slit-like  opening 

of  windpipe  which  is  so  narrow  as  to  prevent  food  falling 

into  the  windpipe. 


Fig.  303.  —  Head  of  Woodpecker, 

c,  tongue;  a,  b,  d,  hyoid  bone;  e,  q.  wind 
pipe;  /,  salivary  gland. 


BIRDS 


163 


The  Internal  Organs,  or  Viscera  (Figs.  304  and  305). 
—  The  viscera  (vis'se-ra),  as  in  most  vertebrates,  include 
the  food  tube  and  its  glands ;  the  lungs,  the  heart,  and 
larger  blood  vessels;  the  kidneys  and  bladder  and  the 
reproductive  organs.  The  lower  part,  or  gullet,  is  en- 
larged into  a  crop.     It  is  largest  in  grain-eating  birds.     It 


Fig.  304.  —  Anatomy  of  Dove  x%. 

bk,  keel  of  breastbone;  G,  g,  brain;  Ir, 
windpipe;  hi,  lung;  A,  heart;  sr,  gul- 
let; k,  crop;  dr,  glandular  stomach; 
mm,  gizzard;  d,  intestine;  n,  kidney; 
///,  ureter;  eil,  openings  of  ureter  and 
egg  duct  into  cloaca,  kl. 


Fig.  305.  —  Food  Tube  of  Bird. 

P,  pancreas;    C,  caeca. 
Question:    Identify  each  part  by  means 
of  Fig.  304. 


is  found  in  the  V-shaped  depression  at  the  angle  of  the 
wishbone,  just  before  the  food  tube  enters  the  thorax. 
The  food  is  stored  and  softened  in  the  crop.  From  the 
crop  the  food  passes  at  intervals  into  the  glandular  stomach. 
Close  to  this  is  the  muscular  stomach,  or  gizzard.  Are  the 
places  of  entrance  and  exit  on  opposite  sides  of  the  gizzard, 
or  near  together  ?    (Fig.  304.)    Is  the  lining  of  the  gizzard 


164 


AXIMAL   BIOLOGY 


rough  or  smooth  ?  Why?  Is  the  gizzard  tough  or  weak? 
Why  are  small  stones  in  the  gizzard  ?  Why  do  not  hawks 
and  other  birds  of  prey  need  a  muscular  gizzard  ?  The 
liver  and  pancreas  empty  their  secretions  into  the  intestines 
by  several  ducts  a  little  way  beyond  the  gizzard.  Beyond 
the    mouths    of    two    caeca   (Fig.    305)   the    many-coiled 

intestine  empties  into  the  straight 
rectum,  which  terminates  in  a 
widened  part  called  the  cloaca. 
Not  only  the  intestine,  but  the 
two  ureters  of  the  urinary  system 
and  the  two  genital  ducts  of  the 
reproductive  system  all  empty  into 
the  cloaca  (Figs.  304,  305). 

The  lungs  have  their  rear  sur- 
faces attached  to  the  spinal 
column  and  ribs  (///,  Fig.  304). 
They  are  connected  with  thin- 
walled,  transparent  air  sacs  which 
aid  in  purifying  the  blood.  When 
inflated  with  warm  air,  they  prob- 
ably make  the  body  of  the  bird 
more  buoyant.  For  the  names, 
location,  and  shape  of  several 
pairs  of  air  sacs,  see  Fig.  306. 
The  connection  of  the  air  sacs  with 
hollows  in  the  humerus  bones  is  also  shown  in  the  figure. 
Many  of  the  bones  are  hollow ;  this  adds  to  the  buoyancy  of 
the  bird.  The  pulmonary  artery,  as  in  man,  takes  dark 
blood  to  the  lungs  to  exchange  its  carbon  dioxide  for 
oxygen.  Of  two  animals  of  the  same  weight,  which  ex- 
pends more  energy,  the  one  that  flies,  or  the  one  that  runs 
the  same  distance  ?       Does  a   bird  require   more  oxygen 


Fig.  306.— Position  of  Lungs 
and  Air  Sacs  (Pigeon). 

7V,  windpipe;  P,  lungs;  Lm,  sac 
under  clavicle  with  prolongation 
{Lh)  into  humerus;  La,  sacs  in 
abdomen. 


BIRDS 


I65 


Fig.  307.  —  Position  of  Vocal 
Cords  (sir)  of  Mammal  and  Bird. 

Question  :  Does  a  fowl  ever  croak  after 
its  head  and  part  of  its  neck  are  cut  off? 
Explain. 


or  less,  in  proportion  to  its  weight,  than  an  animal  that 
lives  on  the  ground  ?  Are  the  vocal  cords  of  a  bird 
higher  or  lower  in  the  wind- 
pipe than  those  of  a  man? 
(Fig.  307.) 

The  heart  of  a  bird,  like  a 
man's  heart,  has  four  cham- 
bers ;  hence  it  keeps  the 
purified  blood  separate  from 
the  impure  blood.  Since 
pure  blood  reaches  the  or- 
gans of  a  bird,  oxidation  is 
more  perfect  than  in  the 
body  of  any  animals  yet 
studied.  Birds  have  higher 
temperature  than  any  other  class  of  animals  whatsoever. 
Tell  how  the  jaws,  tail,  and  wings  of  the  fossil  bird 
Archaeopteryx  differed  from  living  birds  (Fig.  290). 

Suggestions. —  In  the  field  work,  besides  seeking  the  answers  to 
definite  questions,  pupils  may  be  required  to  hand  in  a  record  of  the 
places  and  times  of  seeing  a  certain  number  of  birds  (20  to  40),  with 
the  actions  and  features  which  made  each  distinguishable.  Also,  and 
more  important,  each  pupil  should  hand  in  a  record  of  a  careful  and 
thorough  outdoor  study  of  one  common  species  (see  below)  as  regards 
habits,  nesting,  relation  to  environment,  etc. 

Field  Study  of  a  Common  Species.  —  (For  written  report.) 
Name  of  species.  Haunts.  Method  of  locomotion  when  not 
flying.    Fixing  (rate,  sailing,  accompanying  sound  if  any,  soaring). 

What  is  the  food?  How  obtained?  Association  with  birds  of 
its  own  species.     Relation  to  birds  of  other  species. 

Where  does  it  build  its  nest ?  Why  is  such  a  situation  selected? 
Of  what  is  the  nest  built?  How  is  the  material  carried,  and 
how  built  into  the  nest?     Does    the  bird's  body  fill  the  nest? 

Describe  the  eggs.  Does  the  male  bird  ever  sit  or  otherwise 
assist   female   before   hatching?      Does  it  assist  after   hatching? 


166 


ANIMAL  BIOLOGY 


mm  i  "w 


How  long  is  taken  to  lay 
a  sitting  of  eggs?     How 
long  before  the  birds  are 
hatched?     When  hatched 
are  they  helpless?  Blind? 
Feathered?     (Figs.  301, 
302.)       Do      the     nest- 
lings require  much  food  ? 
How  many  times  is  food 
brought     in     an     hour? 
How  distributed?     Even 
if   the    old    birds    some- 
times  eat  fruit  do   they 
take  fruit  to  the  young? 
What  do  they  feed  to  the 
young?     How   long   be- 


Fig.  308.  —  European  Tomtit's  Nest 
What  are  the  advantages  of  its  shape  ? 

fore    they   leave    the    nest?        [  Jf 
Do  the  parents  try  to  teach  'U 

them  to  fly?  Do  the  par- 
ents care  for  them  after  the 
nest  is  left  ?  What  songs  or 
calls  has  the  bird? 

General    Field    Study. 

(For written  report.}  Name 
the  best  and  poorest  flyers 
you  know;  birds  that  fly 
most  of  the  time  ;  birds  that 
seldom  fly.  Observe  birds 
that  pair;  live  in  flocks. 
Does  their  sociability  vary 
with  the  season?  Do  you 
ever   see   birds  quarreling? 


Fig.  309.  — Tailor  Bird's  Nest  (India). 

Instinct  for  nest  building  highly  perfected. 


BIRDS 


167 


Fighting?  What  birds  do  you  observe  whipping  or  driving  birds 
larger  than  themselves?  Which  parent  do  young  birds  most  re- 
semble? Name  the  purposes  for  which  birds  sing.  Which  senses 
are  very  acute?  Why?  Dull?  Why?  Can  you  test  your  state- 
ments by  experiment?  A  partridge  usually  sits  with  iS  to  24 
eggs  in  nest.  About  how  long  after  laying  first  egg  before  sitting 
begins?     Do  several  partridge  hens  lay  in  the  same  nest? 

Haunts.  —  Name  some  birds  that  are  found  most  often  in 
the  following  localities  :  about  our  homes,  in  gardens  and  or- 
chards, fields  and  meadows, 
in  bushes,  in  the  woods, 
in  secluded  woods,  around 
streams  of  water,  in  thick- 
ets, in  pine  woods. 

Size.  —  Name  birds  as 
large  as  a  robin  or  larger, 
nearly  as  large,  half  as  large, 
much  smaller. 

Colors.  —  Which  sex  is 
more  brilliant?  What  ad- 
vantage are  bright  colors  to 
one  sex?  What  advantage 
are  dull  colors  to  the  other 
sex?  Which  have  yellow  breasts,  red  patch  on  heads,  red  or 
chestnut  breasts,  blue  backs,  black  all  over? 

Habits.  —  Name  the  birds  that  walk,  jump,  swim,  live  in  flocks, 
sing  while  flying,  fly  in  undulations,  in  circles,  have  labored  flight. 

Such  books  as  Wright's  "Birdcraft"  (Macmillan,  N.  Y.),  Clark's 
"Birds  of  Lakeside  and  Prairie"  (Mumford,  Chicago),  and  Pear- 
son's "Stories  of  Bird  Life"  (B.  F.  Johnson,  Richmond),  will  be 
of  great  help.  The  last  book  is  delightfully  written,  and  is  one  of 
the  few  treating  of  bird  life  in  the  South. 

Economic  Importance  of  Birds.  —  Farmers  find  their 
most  valuable  allies  in  the  class  aves,  as  birds  are  the  dead- 
liest enemies  of  insects  and  gnawing  animals.  To  the  in- 
numerable robbers  which  devastate  our  fields  and  gardens, 
nature  opposes  the  army  of  birds.    They  are  less  numerous 


Fig.  310.  —  House  Wren. 


1 68 


ANIMAL   BIOLOGY 


than  insects  and  other 
robbers,  it  is  true,  but 
they  are  skillful  and 
zealous  in  pursuit,  keen 
of  eye,  quick,  active, 
and  remarkably  vora- 
cious. The  purely  in- 
sectivorous birds  are 
the  most  useful,  but  the 
omnivorous  and  grami- 
nivorous birds  do  not 
disdain  insects.  The 
percJicrs  and  the  wood- 
Fig.  311.  -Screech  Owl  (Megascops  asio).        peckers   sJlOllld  be  pro- 

Question:    Compare  posture  of  body,  position  of        teded      1HOSt      CCll'efltllV- 
eyes,  and  size  of  eyes,  with  other  birds.  t-,,  .....  . 

I  he  night  birds  of  prey 
(and  those  of  the  day  to  a  less  degree)  are  very  destructive 
to  field  mice,  rabbits,  and  other 
gnawing  animals.  Some  igno- 
rant farmers  complain  continu- 
ally about  the  harm  done  by 
birds.  To  destroy  them  is  as 
unwise  as  it  would  be  to  destroy 
the  skin  which  protects  the  hu- 
man body  because  it  has  a  spot 
upon  it !  It  cannot  be  repeated 
too  plainly  that  to  hunt  useful 
birds  is  a  wrong  and  mischievous 
act,  and  it  is  stupid  and  barba- 
rous to  destroy  their  nests. 

Injurious    birds  are  few.     Of 

course  birds  which  are  the  ene- 

Fig.  312.  —  Goshawk, 
mies  of  other  birds  are  enemies  Qr  chicken  hawk 


BIRDS 


169 


>V^-,. ■.;;/.,.>,  ,  : 


A\  r 

Fig.  313.  —  Road  Runner,  or  chaparral  bird  (Tex.  to  Cal.). 
(Key,  p.  177.) 


What  order? 


of  mankind,  but  examples  are  scarce  (some  owls  and 
hawks).  Many  birds  of  prey  are  classed  thus  by  mistake. 
Sparrow  hawks,  for  instance,  do  not  eat  birds  except  in 
rare  instances;  they  feed  chiefly  upon  insects.  A  sparrow 
hawk  often  keeps  watch  over  a  field  where  grasshoppers 
are  plentiful  and  destroys  great  numbers  of  them.  When 
a  bird  is  killed  because  it  is  supposed  to  be  injurious,  the 
crop  should  always  be  examined,  and  its  contents  will  often 
surprise  those  who  are  sure  it  is  a  harmful  bird.  The 
writer  once  found  two  frogs,  three  grasshoppers,  and  five 
beetles  that  had  been  swallowed  by  a  "  chicken  hawk " 
killed  by  an  irate  farmer,  but  no  sign  of  birds  having  been 
used  for  food.  Fowls  should  not  be  raised  in  open  places, 
but  among  trees  and  bushes,  where  hawks  cannot  swoop. 
Birds  which  live  exclusively  upon  fish  are,  of  course, 
opposed  to  human  interests.  Pigeons  are  destructive  to 
grain  ;  eagles  feed  chiefly  upon  other  birds. 

If  the  birds  eat  the  grapes,  do  not  kill  the  birds,  but  plant 
more  grapes.    People  with  two  or  three  fruit  trees  or  a  small 


lyo 


ANIMAL    BIOLOGY 


garden  arc  the  only  ones  that  lose  a  noticeable  amount  of 
food.  We  cut  down  the  forests  from  which  the  birds  ob- 
tain part  of  their  food.  We  destroy  insect  pests  at  great 
cost  of  spraying,  etc.  The  commission  the  birds  charge 
for  such  work  is  very  small  indeed.     (See  pages  177-183.) 


Fig.  314.  —  Wood  Duck,  male  {Aix  sponsa).     Nests  in  hollow  trees  throughout 
North  America.    Also  called  summer  duck  in  South.     Why  ? 

The  English  sparrow  is  one  bird  of  which  no  good  word 
may  be  said.  Among  birds,  it  holds  the  place  held  by  rats 
among  beasts.  It  is  crafty,  quarrelsome,  thieving,  and  a 
nuisance.  It  was  imported  in  1852  to  eat  moths.  The 
results  show  how  ignorant  we  are  of  animal  life,  and  how 
slow  we  should  be  to  tamper  with  the  arrangements  of 
nature.  In  Southern  cities  it  produces  five  or  six  broods 
each  year  with  four  to  six  young  in  each  brood.  (Notice 
what  it  feeds  its  young.)  It  fights,  competes  with  and 
drives  away  our  native  useful  birds.  It  also  eats  grain  and 
preys  upon  gardens.     They  have  multiplied  more  in  Aus- 


BIRDS 


171 


tralia  and  the  United  States  than  in  Europe,  because  they 
left  behind  them  their  native  enemies  and  their  new  ene- 
mies (crows,  jays,  shrikes,  etc.)  have  not  yet  developed,  to 
a  sufficient  extent,  the  habit  of  preying  upon  them.  Nature 
will,  perhaps,  after  a  long  time,  restore  the  equilibrium 
destroyed  by  presumptuous  man. 

Protection  of  Birds. —  1.  Leave  as  many  trees  and  bushes 
standing  as  possible.     Plant  trees,  encourage  bushes. 

2.  Do  not  keep  a  cat.  A  mouse  trap  is  more  useful  than 
a  cat.     A  tax  should  be  imposed  upon  owners  of  cats. 

3.  Make  a  bird  house  and  place  on  a  pole;  remove 
bark  from  pole  that  cats  may  not  climb  it,  or  put  a  broad 
band  of  tin  around  the  pole. 

4.  Scatter  food  in  winter.  In  dry  regions  and  in  hot 
weather  keep  a  shallow  tin  vessel  containing  water  on  the 
roof  of  an  outhouse,  or  out-of-the-way  place  for  shy  birds. 

5.  Do  not  wear  feathers  obtained  by  the  killing  of  birds. 
What  feathers  are  not  so  obtained  ? 

6.  Report  all  violators  of  laws  for  protection  of  birds. 

7.  Destroy  English  sparrows. 

Migration.  —  Many  birds,  in  fact  most  birds,  migrate  to 
warmer  climates  to  spend  the  winter.  Naturalists  were 
once  content  to  speak  of  the  migra- 
tion of  birds  as  a  wonderful  instinct, 
and  made  no  attempt 
to  explain  it.  As 
have  the  warmest  covering 
all  animals,  the  winter  mi- 
gration is  not  for  the  pur- 
pose of  escaping  the  cold  ;  it 
is  probably  to  escape  starva- 
tion, because  in  cold  countries  food  is  largely  hidden  by 
snow  in  winter.     On  the  other  hand,  if  the  birds  remained 


Fig.  315.  — Great  Blue  Heron. 
In  flight,  balancing  with  legs. 


\J2 


ANIMAL    BIOIxHiY 


in  the  warm  countries  in  summer,  the  food  found  in  north- 
ern countries  in  summer  would  be  unused,  while  they 
would  have  to  compete  with  the  numerous  tropical  birds 
for  food,  and  they  and  their  eggs  would  be  in  danger  from 
snakes,  wild  cats,  and  other  beasts  of  prey  so  numerous  in 
warm  climates.  These  are  the  best  reasons  so  far  given 
for  migration. 

The  manner  and  methods  of  migration  have  been  studied 
more  carefully  in  Europe  than  in  America.     Migration  is 


FlG.  316.  —  European  Swallows  (Hirnndo  urbica),  assembling  for  autumn 
flight  to  South. 

not  a  blind,  infallible  instinct,  but  the  route  is  learned  and 
taught  by  the  old  birds  to  the  young  ones  ;  they  go  in 
flocks  to  keep  from  losing  the  way  (Fig.  316);  the  oldest 
and  strongest  birds  guide  the  flocks  (Fig.  317).  The  birds 
which  lose  their  way  are  young  ones  of  the  last  brood,  or 
mothers  that  turn  aside  to  look  for  their  strayed  young. 
The  adult  males  seldom  lose  their  way  unless  scattered 
by  a  storm.  Birds  are  sometimes  caught  in  storms  or 
join  flocks  of  another  species  and  arrive  in  countries 
unsuited  for  them,  and  perish.      For  example,   a   sea  or 


BIRDS 


173 


marsh  bird  would  die  of  hunger  on  arriving  in  a  very  dry- 
country. 

The  landmarks  of  the  route  are  mountains,  rivers,  valleys, 
and  coast  lines.  This  knowledge  is  handed  down  from  one 
generation  to  another.  It  includes  the  location  of  certain 
places  on  the  route  where  food  is  plentiful  and  the  birds 
can  rest  in  security.  Siebohm  and  others  have  studied 
the  routes  of  migration  in  the  Old 
World.  The  route  from 
the  nesting  places  in 
northern  Eu- 
Africa  fol-  <,/         «~*>     *^  roPe  t0 

lows  the  Rhine, 
the    Lake    of    Geneva, 
the  Rhone,  whence  some  spe- 
cies follow  the  Italian  and  others  the  Span- 
ish coast  line  to  Africa.     Birds  choose  the 
lowest  mountain  passes.     The  Old  World 
martin  travels  every  year  from  the  North 
Cape  to  the  Cape  of  Good  Hope  and  back  again  !    An- 
other route  has  been  traced  from  Egypt  along  the  coast 
of  Asia  Minor,  the  Black  Sea  and  Ural  Mts.  to  Siberia. 

Field  Study  of  Migration.  — Three  columns  may  be  filled 
on  the  blackboard  in  an  unused  corner,  taking  several 
months  in  spring  or  fall  for  the  work.  First  column,  birds 
that  stay  all  the  year.  Second  column,  birds  that  come 
from  the  south  and  are  seen  in  the  summer  only.  Third 
column,  birds  that  come  from  the  north  and  are  seen  in 
winter  only.  Exact  dates  of  arrival  and  departure  and 
flight  overhead  should  be  recorded  in  notebooks.  Many 
such  records  will  enable  American  zoologists  to  trace  the 
migration  routes  of  our  birds.  Reports  may  be  sent  to  the 
chief  of  the  Biological  Survey,  Washington,  D.C. 


Fig.  317.  —  Cranes 
Migrating,  with 
leader  at  point  of 
V-shaped  line. 


174 


ANIMAL   BIOLOGY 


Molting.  —  How  do  birds  arrange   their   feathers  after 
they    have   been   ruffled?      Do   they  ever  bathe  in  water  ? 


Fig.  318.  —  Aptekyx,  of  New  Zealand.     Size  of  a  hen,  wings  and  tail 
rudimentary,  feathers  hair-like. 

In  dust  ?     Dust  helps  to  remove  old  oil.     At  what  season 
are  birds  brightest  feathered  ?    Why  ?    Have  you  ever  seen 


& 


Fig.  319. —  Golden,  Silver,  and  Noble  Pheasants,  males.  Order? 
(Key,  p.  177.)  Ornaments  of  males,  brightest  in  season  of  courtship,  are  due  to 
sexual  selection  (Figs.  321-7-9,  333). 

evidence  of  the  molting  of  birds  ?     Describe  the  molting 
process  (page  120). 


BIRDS 


175 


Fig.  320. 
Cockatoo. 


Adaptations  for 
Flying.  —  Flight 
is  the  most  diffi- 
cult and  energy- 
consuming  meth- 
od of  moving 
found  among  ani- 
mals, and  care- 
ful adjustment  is 
necessary.  For 
balancing,  the 
heaviest  muscles 
are  placed  at  the 
lower  and  central 
portion  of  the  body. 
These  are  the  flying 
muscles,  and  in  some 
birds  (humming  birds) 
they  make  half  of  the 
entire  weight.  Teeth 
are  the  densest  of  ani- 
mal structures ;  teeth 
and  the  strong  chew- 
ing muscles  required 
would  make  the  head 
heavy  and  balancing 
difficult ;  hence  the  chewing  apparatus  is 
transferred  to  the  heavy  gizzard  near  the 
center  of  gravity  of  the  body.  The  bird's 
neck  is  long  and  excels  all  other  necks  in 
flexibility,  but  it  is  very  slender  (although 
apparently  heavy),  being  inclosed  in  a 
loose,  feathered  skin.     A  cone  is  the  best 


Fig.  321.  —  Bird  01 
Paradise  (Asia). 


176 


A.XIMAL   BIOLOGY 


shape  to  enable  the  body  to  penetrate  the  air,  and  a  small 
neck  would  destroy  the  conical  form.  The  internal  organs 
are  compactly  arranged  and  rest  in  the  cavity  of  the  breast 
bone.  The  bellows-like  air  sacs  filled  with  warm  air 
lighten  the  bird's  weight.  The  bones  are  hollow  and  very 
thin.  The  large  tail  quills  are  used  by  the  bird  only  in 
guiding  its  flight  up  and  down,  or  balancing  on  a  limb. 

The  feet  also  aid  a 
flying  bird  in  bal- 
ancing. The  wing 
is  so  constructed  as 
to  present  to  the 
air  a  remarkably 
large  surface  com- 
pared with  the 
small  bony  support 
in  the  wing  skele- 
ton. Are  tubes 
ever  resorted  to  by 
human  architects  when  lightness  combined  with  strength 
is  desired  ?  Which  quills  in  the  wing  serve  to  lengthen 
it?  (Fig.  296.)  To  broaden  it?  Is  flight  more  difficult 
for  a  bird  or  a  butterfly  ?  Which  of  them  do  the  flying 
machines  more  closely  resemble?  Can  any  bird  fly  for  a 
long  time  without  flapping  its  wings  ? 


Fig.  322. —  Herring  Gull.    (Order?) 


Exercise  in  the  Use  of  the  Key.  —  Copy  this  list  and  write  the  name 
of  the  order  to  which  each  of  the  birds  belongs.     (Key,  page  177.) 

Cockatoo  (Fig.  320)       Wren  (Fig.  310)  Pheasant  (Fig.  319) 

Sacred  Ibis  (Fig.  328)    Apteryx  (Fig.  318)  Wood  Duck  (Fig.  314) 

Screech  Owl  (Fig.  311)    Lyre  bird  (Fig.  327)  Jacana  (Fig.  324) 

Nightingale  (Fig.  325)    Road  Runner  (Fig.  313)  Sea  Gull  (Fig.  322) 

Top-knot    Quail    (Fig.   Ostrich  (Fig.  332)  Heron  (Fig.  315) 

329)  Penguin  (Fig.  330)  Hawk  (Fig.  312) 


BIRDS 


1 77 


KEY,    OR   TABLE,    FOR    CLASSIFYING    BIRDS  {Class  Aves) 
INTO    ORDERS 


A j  Wings  not  suited  for  flight,  2  or  3  toes 
Aj  Wings  suited  for  flight  (except  the  penguin) 
B[  Toes  united  by  a  web  for  swimming,  legs  short 
Cj  Feet  placed  far  back  ;  wings  short,  tip  not 

reaching  to  base  of  tail  (Fig.  300) 
C,  Bill  flattened,  horny  plates  under  margin 

of  upper  bill  (Fig.  323) 
C3  Wings  long  and  pointed,  bill  slender 
C4  All   four   toes    webbed,    bare   sac   under 
throat 
B.,  Toes  not  united  by  web  for  swimming 
C,  Three  front  toes,  neck  and  legs  long,  tibia 

(shin,  or  ••  drumstick  ")  partly  bare 
C2  Three  front  toes,  neck  and  legs  not  long 
Dj  Claws  short  and  blunt  (e,  Fig.  300) 
Ej  Feet  and  beak  stout,  young  feathered, 

base  of  hind  toe  elevated 
E„  Feet  and  beak  weak,  young  naked 
D„   Claws   long,   curved    and   sharp,   bill 

hooked  and  sharp 
D3  Claws  long,  slightly  curved,  bill  nearly 
straight 
C3  Two  front  and  two  hind  toes  (Fig.  300) 
Dj  Bill  straight,  feet  used  for  climbing 
D1  Bill  hooked,  both  bill  and  feet  used  for 
climbing 


Orders 

Runners 


Divers 

Bill-strainers 

Sea-fliers 
Gorgers 


Waders 


scratchers 

Messengers 
Robbers 

Perchers 


foot-climbers 
Bill-climbers 


The  Food  of  Birds.  —  Extracts  from  Bulletin  No.  54 
(United  States  Dept.  of  Agriculture),  by  F.  E.  L.  Beal. 

The  practical  value  of  birds  in  controlling  insect  pests  should 
be  more  generally  recognized.  It  may  be  an  easy  matter  to 
exterminate  the  birds  in  an  orchard  or  grain  field,  but  it  is  an 
extremely  difficult  one  to  control  the.  insect  pests.  It  is  certain, 
too,  that  the  value  of  our  native  sparrows  as  weed  destroyers  is 
not  appreciated.  ^Yeed  seed  forms  an  important  item  of  the 
winter  food  of  many  of  these  birds,  and  it  is  impossible  to  estimate 
the  immense  numbers  of  noxious  weeds  which  are  thus  annually 

N 


i  ;8 


ANIMAL    BIOLOGY 


destroyed.     If  crows  or  blackbirds  are   seen   in   numbers  about 

cornfields,  or  if  woodpeckers  are  noticed  at  work  in  an  orchard, 
it  is  perhaps  not  surprising  that  they 
are  accused  of  doing  harm.  Careful  in- 
vestigation, however,  often  shows  that 
they  are  actually  destroying  noxious  in- 
sects ;  and  also  that  even  those  which 
do  harm  at  one  season  may  compensate 
for  it  by  eating  insect  pests  at  another. 
Insects  are  eaten  at  all  times  by  the 
majority    of    land    birds.       During    the 

breeding  season  most  kinds  subsist  largely  on  this  food,  and  rear 

their  young  exclusively  upon  it. 

Partridges.  —  Speaking  of  13  birds  which  he  shot,  Dr.  Judd  says  : 

These   13  had  taken  weed  seed  to  the  extent  of  63  per  cent  of 


Fig.  323.  — Head  of  Duck. 


FIG.  324.  —  JACANA.     (Mexico,  Southwest  Texas,  and  Florida.) 
Questions:    What  appears  to  be  the  use  of  such  long  toes?    What  peculiarity  of  wing?  head? 

their  food.  Thirty-eight  per  cent  was  ragweed,  2  per  cent  tick 
trefoil,  partridge  pea,  and  locust  seeds,  and  23  per  cent  seeds  of 
miscellaneous  weeds.     About  14  per  cent  of  the  quail's  food  for 


BIRDS 


I  79 


the  year  consists  of  animal  matter  (insects  and  their  allies). 
Prominent  among  these  are  the  Colorado  potato  beetle,  the 
striped  squash  beetle,  the  cottonboll-weevil,  grasshoppers.  As  a 
weed  destroyer  the  quail  has  few,  if  any,  superiors.  Moreover, 
its  habits  are  such  that  it  is  almost  constantly  on  the  ground, 
where  it  is  brought  in  close  contact  with  both  weed  seeds  and 
ground-living  insects.  It  is  a  good  ranger,  and,  if  undisturbed,  will 
patrol  every  day  all  the  fields  in  its  vicinity  as  it  searches  for  food. 


Fig.  325.— Nightingale,  x  \.  Fig.  326.  — Skylark,  x  \. 

Two  celebrated  European  songsters. 

D0yes.  —  The  food  of  the  dove  consists  of  seeds  of  weeds, 
together  with  some  grain.  The  examination  of  the  contents  of 
237  stomachs  shows  that  over  99  per  cent  of  the  food  consists 
wholly  of  vegetable  matter. 

Cuckoos.  —  An  examination  of  the  stomachs  of  46  black-billed 
cuckoos,  taken  during  the  summer  months,  showed  the  remains 
of  906  caterpillars,  44  beetles,  96  grasshoppers,  100  sawflies,  30 
stink  bugs,  and  15  spiders.  Of  the  yellow-billed  cuckoos,  or 
"  rain-crow,"  109  stomachs  collected  from  May  to  October,  in- 
clusive, were  examined.  The  contents  consisted  of  1,865  cater- 
pillars, 93  beetles,  242  grasshoppers,  37  sawflies,  69  bugs,  6  flies, 
and  86  spiders. 


lSo 


A.XIMAL   BIOLOGY 


, 


Woodpeckers.  —  Careful  observers  have  noticed  that,  excepting 
a  single  species,  these  birds  rarely  leave  any  conspicuous  mark  on 
a  healthy  tree,  except  when  it  is  affected  by  wood-boring  larvae, 
which  are  accurately  located,  dis- 
lodged, and  devoured  by  the  wood- 
pecker. Of  the  flickers'  or  yellow- 
hammers'  stomachs  examined,  three 
were  completely  filled  with  ants. 
Two  of  the  birds  each 
contained  more  than 
3,000  ants,  while  the 
third  bird  contained  fully 
5,000.  These  ants  be- 
long to  species  which 
live  in  the  ground.  It  is 
these  insects  for  which 
the  flicker  is  reaching 
when  it  runs  about  in  the 
grass.  The  yellow-bellied 
woodpecker  or  sapsucker 
(Sphyrapicus  varius)  was  shown  to  be  guilty  of  pecking  holes  in 
the  bark  of  various  forest  trees,  and  sometimes  in  that  of  apple 

trees,  and  of  drinking  the 
sap  when  the  pits  became 
filled.  It  has  been  proved, 
however,  that  besides  tak- 
ing the  sap  the  bird  cap- 
tures large  numbers  of 
insects  which  are  attracted 
by  the  sweet  fluid,  and 
that  these  form  a  very 
considerable  portion  of 
its  diet.  The  woodpeck- 
ers seem  the  only  agents 
Fig.  328.     Sacred  Ibis.    rOrder?)  whjch     can     successfully 

cope  with  certain  insect  enemies  of  the  forests,  and,  to  some 
extent,  with  those  of  fruit  trees  also.  For  this  reason,  if  for  no 
other,  they  should  be  protected  in  every  possible  way. 


Fin.  327. 


WMkh 


BIRDS 


181 


The  night  hawk,  or  "  bull  bat,"  may  be  seen  most  often  soaring 
high  in  air  in  the  afternoon  or  early  evening.  It  nests  upon  rocks  or 
bare  knolls  and  flat  city  roofs.  Its  food  consists  of  insects  taken 
on  the  wing ;  and  so  greedy  is  the  bird  that  when  food  is  plentiful, 
it  fills  its  stomach  almost  to  bursting.  Ants  (except  workers)  have 
wings  and  fly  as  they  are  preparing  to  propagate.  In  destroying 
ants  night  hawks  rank  next  to,  or  even  with,  the  woodpeckers,  the 
acknowledged  ant-eaters  among  birds. 


Kfe     'A'V'i. 


FlG.  329.  —  Top-knot  Quail,  or  California  Partridge. 
(West  Texas  to  California.) 

The  kingbird,  or  martin,  is  largely  insectivorous.  In  an  ex- 
amination of  62  stomachs  of  this  bird,  great  care  was  taken  to 
identify  every  insect  or  fragment  that  had  any  resemblance  to  a 
honeybee ;  as  a  result,  30  honeybees  were  identified,  of  which  29 
were  males  or  drones  and  1  was  a  worker. 

Blue  Jay.  —  In  an  investigation  of  the  food  of  the  blue  jay  300 
stomachs  were  examined,  which  showed  that  animal  matter  com- 
prised 24  per  cent  and  vegetable  matter  76  per  cent  of  the  bird's 
diet.  The  jay's  favorite  food  is  mast  {i.e.  acorns,  chestnuts, 
chinquapins,  etc.),  which  was  found  in  200  of  the  300  stomachs, 
and  amounted  to  more  than  42  per  cent  of  the  whole  food. 


182 


A XI MAI.    BIOLOGY 


are  these  all  of  his  sins. 


Fig.  330.—  Penguin  of  Pata 
GONIA.  Wings  used  hs  flip 
pers  for  swimming. 


Crow.  —  That  he  does  pull  up  sprouting  corn,  destroy  chickens, 
and  rob  the  nests  of  small  birds  has  been  repeatedly  proved.  Nor 
He  is  known  to  eat  frogs,  toads,  sala- 
manders, and  some  small  snakes,  all 
harmless  creatures  that  do  some  good 
by  eating  insects.  Experience  has 
shown  that  they  may  be  prevented 
from  pulling  up  young  corn  by  tarring 
the  seed,  which  not  only  saves  the 
corn  but  forces  them  to  turn  their  at- 
tention to  insects.  May  beetles,  "  dor- 
bugs,"  or  June  bugs,  and  others  of 
the  same  family  constitute  the  princi- 
pal food  during  spring  and  early  sum- 
mer, and  are  fed  to  the  young  in 
immense  quantities. 

Ricebird.  —  The  annual  loss  to  rice 
growers  on  account  of  bobolinks  has 
been  estimated  at  $2,000,000. 

Meadow  Lark.  —  Next  to  grasshop- 
pers, beetles  make  up  the  most  impor- 
tant item  of  the  meadow  lark's  food, 
amounting  to  nearly  21  per  cent. 
May  is  the  month  when  the  dreaded 
cut-worm  begins  its  deadly  career,  and 
then  the  lark  does  some  of  its  best 
work.  Most  of  these  caterpillars  are 
ground  feeders,  and  are  overlooked 
by  birds  which  habitually  frequent 
trees,  but  the  meadow  lark  finds  and 
devours  them  by  thousands. 
Sparrows.  —  Examination  of  many  stomachs  shows  that  in 
winter  the  tree  sparrow  feeds  entirely  upon  seeds  of  weeds. 
Probably  each  bird  consumes  about  one  fourth  of  an  ounce  a 
day.  Farther  south  the  tree  sparrow  is  replaced  in  winter  by  the 
white-throated  sparrow,  the  white-crowned  sparrow,  the  fox  spar- 
row, the  song  sparrow,  the  field  sparrow,  and  several  others ;  so 
that  all  over  the  land  a  vast  number  of  these  seed  eaters  are  at 


FlG.  331.  —  Umbrella  holding 
the  nests  of  social  weaver 
bird  of  Africa ;    polygamous. 


BIRDS 


183 


work  during  the  colder  months  reducing  next  year's  crop  of  worse 
than  useless  plants. 

Robin. — An  examination  of  500  stomachs  shows  that  over 
42  per  cent  of  its  food  is  animal  matter,  principally  insects, 
while  the  remainder  is  made  up  largely  of  small  fruits  or 
berries.  Vegetable  food  forms  nearly  58  per  cent  of  the  stom- 
ach contents,  over  47  per  cent  being  wild  fruits,  and  only  a 
little  more  than  4  per  cent  being  possibly  cultivated  varieties. 
Cultivated  fruit  amounting  to  about  25  per  cent  was  found 
in  the  stomachs  in  June  and  July,  but  only  a  trifle  in  August. 
Wild  fruit,  on  the  contrary,  is  eaten  in  every 
month,  and  constitutes  during  half  the  year  a 
staple  food. 

Questions.  —  Which  of  these  birds  are  com- 
mon in  your  neighborhood?  Which  of  them 
according  to  the  foregoing  report  are  plainly  inju- 
rious? Clearly  beneficial?  Doubtful?  Which 
are  great  destroyers 
of  weed  seeds? 
Wood-borers?  Ants? 
Grain?  Why  is  the 
destruction  of  an  ant 
by  a  night  hawk  of 
greater  benefit  than 
the  destruction  of  an 
ant  by  a  woodpecker? 
Name  the  only  wood- 
pecker that  injures 
trees.  If  a  bird  eats 
two  ounces  of  grain 
and  one  ounce  of  in- 
sects, has  it  probably 
done  more  good  or 
more  evil? 


Fig.  332. —  African  Ostrich,  x 


(Urder  ?) 


CHAPTER    XIV 

MAMMALS    (BEASTS   AND   MAN) 

Suggestions.  —  A  tame  rabbit,  a  house  cat,  or  a  pet  squirrel  may 
be  taken  to  the  school  and  observed  by  the  class.  Domestic  ani- 
mals may  be  observed  at  home  and  on  the  street.  A  study  of  the 
teeth  will  give  a  key  to  the  life  of  the  animal,  and  the  teacher 
should  collect  a  few  mammalian  skulls  as  opportunities  offer.  The 
pupils  should  be  required  to  identify  them  by  means  of  the  chart 
of  skulls  (p.  194).  If  some  enthusiastic  students  fond  of  anatomy 
should  dissect  small  mammals,  the  specimens  should  be  killed  with 
chloroform,  and  the  directions  for  dissection  usual  in  laboratory 
works  on  this  subject  may  be  followed.  There  is  a  brief  guide  on 
page  223.  The  following  outline  for  the  study  of  a  live  mammal 
will  apply  almost  as  well  to  the  rabbit  or  squirrel  as  to  the  cat. 

The  Cat. — -The  house  cat  (Fclis  dontestica)  is  probably- 
descended  from  the  Nubian  vdX{Felis maniculata,  Fig.  333) 
found  in  Africa.  The  wild  species  is  about  half  again  as 
large  as  the  domestic  cat,  grayish  brown  with  darker 
stripes  ;  the  tail  has  dark  rings.  The  lynx,  or  wild  cat 
of  America  {Lynx  rufits),  is  quite  different.  Compare  the' 
figures  (333,  335)  and  state  three  obvious  differences. 
To  which  American  species  is  the  house  cat  closer  akin, 
the  lynx  (Fig.  335)  or  the  ocelot  (Fig.  334)?  The  domes- 
tic cat  is  found  among  all  nations  of  the  world.  What  is 
concluded,  as  to  its  nearest  relatives,  from  the  fact  that  the 
Indians  had  no  cats  when  America  was  discovered  ?  It 
was  considered  sacred  by  the  ancient  Egyptians,  and  after 
death  its  body  was  embalmed. 

The  body  of  the  cat  is  very  flexible.  It  may  be  divided 
into  five  regions,  the  head,  neck,  trunk,  tail,  and  limbs.     Its 

tSj 


MAMMALS 


185 


Fig.  333.  —  Wild  Cat  of  Africa  {Felts  maniculata),  x  %. 

eyes  have  the  same  parts  as  the  eyes  of  other  mammals. 
Which  part  of  its  eye  is  most  peculiar?  (Fig.  333.)  What 
part  is  lacking  that  is  present  in  birds  ?  How  are  the  eyes 
especially  adapted  for  seeing  at  night  ?  Does  the  pupil  in 
the  light  extend  up  or  down  or  across  the  iris  ?  Does  it 
ever  become  round  ? 

What  is  the  shape  and  position  of  the  ears  ?  Are  they 
large  or  small  compared  with  those  of  most  mammals  ? 
They  are  fitted  best  for  catching  sound  from  what  direc- 
tion ?  What  is  thus  indicated  in  regard  to  the  cat's  habits  ? 
(Compare  with  ears  of  rabbit.)  Touch  the  whiskers  of  the 
cat.  What  result  ?  Was  it  voluntary  or  involuntary  mo- 
tion ?  Are  the  nostrils  relatively  large  or  small  compared 
with  those  of  a  cow  ?     Of  man  ? 

Is  the  neck  long  or  short?  Animals  that  have  long  fore 
legs  usually  have  what  kind  of  a  neck  ?  Those  with  short 
legs?  Why?  How  many  toes  on  a  fore  foot  ?  Hind  foot? 
Why  is  this  arrangement  better  than  the  reverse  ?  Some 
mammals  are  sole  walkers  {plantigrade},  some  are  toe 
walkers    (digitigrade).       To    which    kind    does     the    cat 


1 86 


AXIMAL   BIOLOGY 


\    '     " 


$B&& 


1  IP*^^      '■  ;     .       .  .  '  ,.-^V;../ 

Fie.  334. —  Ocelot  (Felis  partialis),  of  Texas  and  Mexico.     X  £. 

belong  ?  Does  it  walk  on  the  ends  of  the  toes  ?  Does  it 
walk  with  all  the  joints  of  the  toes  on  the  ground  ?  Where 
is  the  heel  of  the  cat?  (Fig.  334.)  The  wrist?  To  make 
sure  of  the  location  of  the  wrist,  begin  above  :  find  the  shoul- 
der blade,  the  upper  arm  (one  or  two  bones?),  the  lower 
arm  (one  or  two  bones?),  the  wrist,  the  palm,  and  the 
fingers  (Fig.  337).     Is  the  heel  bone  prominent  or  small  ? 

In  what  direction  does  the  knee  of  the  cat  point  ?  The 
heel  ?  The  elbow  ?  The  wrist  ?  Compare  the  front  and 
hind  leg  in  length ;  straightness  ;  heaviness  ;  number  and 
position  of  toes ;  sharpness  of  the  claivs.  What  makes  the 
dogs  claivs  duller  than  a  cat's  ?  What  differences  in  habit 
go  with  this  ?  Judging  from  the  toe  that  has  become  use- 
less on  the  fore  foot  of  the  cat,  which  toe  is  lacking  in  the 
hind  foot  ?  Is  it  the  cat's  thumb  or  little  finger  that  does 
not  touch  the  ground?  (Fig.  337.)  Locate  on  your  own 
hand  the  parts  corresponding  to  the  pads  on  the  forefoot 
of  a  cat.     Of  what  use  are  soft  pads  on  a  cat's  foot  ? 

Some  animals  have  short,  soft  fur  and  long,  coarse  over 
hair.  Does  the  cat  have  both  ?  Is  the  cat's  fur  soft  or 
coarse  ?     Does  the  fur  have  a  color  near  the  skin  different 


MAMMALS 


I87 


from  that  at  the  tip  ?  Why  is  hair  better  suited  as  a  cover- 
ing for  the  cat  than  feathers  would  be  ?  Scales  ?  Where 
are  long,  stiff  bristles  found  on  the  cat  ?  Their  length 
suggests  that  they  would  be  of  what  use  to  a  cat  in  going 
through  narrow  places  ?  Why  is  it  necessary  for  a  cat  to 
be  noiseless  in  its  movements  ? 


'<''-  n"JS^> 


m%&%. 


Fig.  335.—  LYNX  [Lynx  rufus).    The  "  Bob-tailed  cat"  (North  America). 

Observe  the  movements  of  the  cat.  —  Why  cannot  a  cat 
come  down  a  tall  tree  head  foremost  ?  Did  you  ever  see  a 
cat  catch  a  bird?  How  does  a  cat  approach  its  prey? 
Name  a  jumping  insect  that  has  long  hind  legs;  an  am- 
phibian; several  mammals  (Figs.  362,  374).  Does  a  cat 
ever  trot  ?  Gallop  ?  Does  a  cat  chase  its  prey  ?  When 
does  the  cat  move  with  its  heel  on  the  ground  ?  The 
claws  of  a  cat  are  withdrawn  by  means  of  a  tendon  (see 
Fig.  338).  Does  a  cat  seize  its  prey  with  its  mouth  or  its 
feet  ? 

How  does  a  cat  make  the  purring  sound  ?  (Do  the  lips 
move  ?     The  sides  ?)     How  does  a  cat  drink  ?     Do  a  cat 


188 


ANIMAL   BIOLOGY 


and  dog  drink  exactly  the  same  way  ?  Is  the  cat's  tongue 
rough  or  smooth  ?  How  is  the  tongue  used  in  getting  the 
flesh  off  close'  to  the  bone  ?  Can  a  cat  clean  a  bone 
entirely  of  meat? 

In  what  state  of  development  is  a  newly  born  kitten? 
With  what  does  the  cat  nourish  its  young?     Name  ten 

animals  of  various  kinds 

young  are  simi- 

nourished.  What 

this  class  of  ani- 

pjj         ^v^k_'  mals  called  ? 


Why  does  a 
cat  bend  its  back 
when  it  is  frightened  or 
angry  ?  Does  a  cat  or  a  dog  eat  a  greater  variety  of  food  ? 
Which  refuses  to  eat  an  animal  found  dead  ?  Will  either 
bury  food  for  future  use  ?  Which  is  sometimes  trouble- 
some by  digging  holes  in  the  garden  ?  Explain  this  in- 
stinct. Which  lived  a  solitary  life  when  wild  ?  Which  had 
a  definite  haunt,  or  home  ?  Why  are  dogs  more  sociable 
than  cats?  A  dog  is  more  devoted  to  his  master.  Why? 
A  cat  is  more  de- 


FiG.  336.  —  Jaguar,  of  tropical  America. 


voted  to  its  home, 
and  will  return  if 
carried  away.  Why? 
Why  does  a  dog 
turn  around  before 
lying  down  ?  (Con- 
sider its  original 
environment.) 
The  Skeleton  (Fi 


Fig.  337.  — Skeleton  of  Cat. 
337).  —  Compare  the  spinal  column 


of  a  cat  in  form  and  flexibility  with  the  spinal  column  of 
a  fish,  a  snake,  and  a  bird. 


MAMMALS 


189 


The  skull  is  joined  to  the  spinal  column  by  two  knobs 
(or  condyls),  which  fit  into  sockets  in  the  first  vertebra. 
Compare  the  jaws  with  those  of  a  bird  and  a  reptile. 
There  is  a  prominent  ridge  in  the  temple  to  which  the 
powerful  chewing  muscles  are  attached.  There  is  also  a 
ridge  at  the  back  of  the  head  where  the  muscles  which 
support  the  head  are  attached  (Fig.  348). 

Count  the  ribs.  Are  there  more  or  fewer  than  in  man  ? 
The  breastbone  is  in  a  number  of  parts,  joined,  like  the 
vertebras,  by  cartilages.  Compare  it  with  a  bird's  ster- 
num ;  why  the  difference  ?  The  shoulder  girdle,  by  which 
the  front  legs  are  attached  to  the 
trunk,  is  hardly  to  be  called  a  gir- 
dle, as  the  collar  bones  (clavicles) 
are  rudimentary.  (They  often  es- 
cape notice  during  dissection,  being 
hidden  by  muscles.)  The  shoulder 
blades,  the  other  bones  of  this  gir- 
dle, are  large,  but  relatively  not  so 
broad  toward  the  dorsal  edge  as 
human  shoulder  blades.  The  clav- 
icles are  tiny  because  they  are  useless.  Why  does  the  cat 
not  need  as  movable  a  shoulder  as  a  man  ?  The  pelvic,  or 
hip  girdle,  to  which  the  hind  legs  are  attached,  is  a  rigid 
girdle,  completed  above  by  the  spinal  column,  to  which  it 
is  immovably  joined.  Thus  the  powerful  hind  legs  are 
joined  to  the  most  rigid  portion  of  the  trunk. 

Mammals. —  The  cat  belongs  to  the  class  Mammalia  or 
mammals.  The  characteristics  of  the  class  are  that  the 
young  are  not  hatched  from  eggs,  but  are  born  alive,  and 
nourished  with  milk  (hence  have  lips),  and  the  skin  is 
covered  with  hair.  The  milk  glands  are  situated  ventrally. 
The    position  of   the    class  in    the   animal   kingdom    was 


Fig.  338. —  Claw   of  Cat 

(1)  retracted  by  ligament,  and 

(2)  drawn    down  by   muscle 
attached  to  lower  tendon. 


190 


ANIMAL   BIOLOGY 


shown  when  the  cow  was  classified  (p.  9).  Their  care  for 
the  young,  their  intelligence,  and  their  ability  to  survive 
when  in  competition  with  other  animals,  causes  the  mam- 
mals to  be  considered  the  highest  class  in  the  animal 
kingdom. 

According  to  these  tests,  what  class  of  vertebrates  should 
rank  next  to  mammals?  Compare  the  heart,  lungs,  blood, 
and  parental  devotion  of  these  two  highest  classes  of  ani- 
mals. 


Fig.  339.  — Skeleton  of  Lion  (cat  family). 

The  first  mammals,  which  were  somewhat  like  small 
opossums,  appeared  millions  of  years  ago,  when  the  world 
was  inhabited  by  giant  reptiles.  These  reptiles  occupied 
the  water,  the  land,  and  the  air,  and  their  great  strength 
and  ferocity  would  have  prevented  the  mammals  from 
multiplying  (for  at  first  they  were  small  and  weak),  but 
the  mammals  carried  their  young  in  a  pouch  until  able  to 
care  for  themselves,  while  the  reptiles  laid  eggs  and  left 
them  uncared  for.  The  first  mammals  used  reptilian  eggs 
for  food,  though  they  could  not  contend  with  the  great 
reptiles.  Because  birds  and  mammals  are  better  parents 
than  reptiles,  they  have  conquered  the  earth,  and  the  rep- 


MAMMALS 


191 


Fig.  340.  —  Walrus  (Trichechus  rosmarus). 


tiles  have  been  forced  into  subordination,  and  have  become 
smaller  and  timid. 

Classification  of  Mammals.  —  Which  two  have  the  closest 
resemblances  in  the  following  lists  :  Horse,  cow,  deer.  Why  ? 
Cat,  cow,  bear.  Why  ?  Monkey,  man,  sheep.  Why  ?  Rat, 
monkey,  squirrel.  Why?  Giraffe,  leopard,  camel.  Why? 
Walrus,  cat,  cow.  Why  ? 
Check  the  five  mammals 
in  the  following  lists  that 
form  a  group  resembling 
each  other  most  closely : 
Lion,  bear,  pig,  clog,  squir- 
rel, cat,  camel,  tiger,  man. 
State  your  reasons.  Gi- 
raffe, leopard,  deer,  cow, 
rat,  camel,  hyena,  horse, 
monkey.    State  reasons. 

Teeth  and  toes  are 
the  basis  for  subdividing 
the  class  mammalia  into 
orders.  Although  the 
breathing,  circulation,  and 
internal  organs  and  pro- 
cesses are  similar  in  all 
mammals,  the  external 
organs  vary  greatly  be- 
cause of  the  varying  en- 
vironments of  different  species.  The  internal  structure 
enables  us  to  place  animals  together  which  are  essentially 
alike  ;  e.g.  the  whale  and  man  are  both  mammals,  since 
they  resemble  in  breathing,  circulation,  and  multiplication 
of  young.  The  external  organs  guide  us  in  separating  the 
class  into  orders.     The  teeth  vary  according  to  the  food 


Fig.  341.  —  Weasel,  in  summer;  in  Canada 
in  winter  it  is  all  white  but  tip  of  tail. 


192 


ANIMAL    BIOLOGY 


b  e 


Fig.  342.  —  Foot  of  Bear 
{Plantigrade). 


eaten.  The  feet  vary  according  to  use  in  obtaining  food 
or  escaping  from  enemies.  This  will  explain  the  differ- 
ence in  the  length  of  legs  of  lion 
and  horse,  and  of  the  forms  of 
the  teeth  in  cat  and  cow.  Make 
a  careful  study  of  the  teeth  and 
limbs  as  shown  in  the  figures  and 
in  all  specimens  accessible.  Write 
out  the  dental  formulas  as  indi- 
cated at  the  top  of  page  194.  The  numerals  above  the  line 
show  the  number  of  upper  teeth ;  those  below  the  line 
show  the  number  of  lower  teeth  in  one  half  of  the  jaw. 
They  are  designated  as  follows  :  I,  incisors ;  C,  canine ; 
M,  molars.  Multiplying  by  two  gives  the  total  number. 
Which  skulls  in  the  chart  have  the  largest  canines  ? 
Why  ?  The  smallest,  or  none  at  all  ?  Why  ?  Compare 
the  molars  of  the  cow,  the  hog,  and  the  dog.  Explain 
their  differences.  In  which  skulls  are  some  of  the  molars 
lacking  ?  Rudimentary  ?  Why  are  the  teeth  that  do  not 
touch  usually  much  smaller  than  those  that  do  ? 


0 

' 

—        — -J 

Fig.  243. —  Polar  Bear  (U?sus  maritimus). 


MAMMALS 


193 


KEY,   OR   TABLE,  FOR   CLASSIFYING   MAMMALS 
{class  Mammalia)    INTO    ORDERS 


Ai   Imperfect  Mammals,  young  hatched  or  pre- 
maturely born 

Bi  Jaws, a  birdlike  beak,  egg-laying 
Bj  Jaws  not  beaklike,  young  carried  in  pouch 
A2   Perfect  Mammals,  young  not  hatched,  nor 
prematurely  born 

'Cj  Front  part  of  both  jaws  lack  teeth 
C2  Teeth  with  sharp  points  for  piercing 

shells  of  insects 
C,  Canines  very  long,  molars  suited  for 

tearing 
.C<  Canines  lacking,  incisors  very  large 

Bo     f 
Digits  I  C1  Head  large  ;   carnivorous 
not    I  C,  Head  small ;  herbivorous 
distinct 


Bi 
Digits 
with 

claws 


B3 

Digits 
■with 
nails 
or 
hoofs 


C1  Five  toes,  nose  prolonged  into  a  snout 

C2  Toes  odd  number,  less  than  five 

C3  Toes  even  number,  upper  front  teeth 

lacking,  chew  the  cud 
C4  Toes  even  number,  upper  front  teeth 

present,  not  cud-chewers 
C5  All  limbs  having  hands 
C„  Two  limbs  having:  hands 


Orders 

Mon'otremes 
Marsu ' pials 

Eden'tates 
Insect'ivors 

Car'nivors 
Rodents 

Ce/a'ceans 
Sire'neans 

Proboscideans 
Equities 

Ru'  minants 

Swine 

Quad' ru  mans 

Bi'  mans 


^ 


Exercise  in  Classification.  —  Copy  the  following  list,   and  by  refer- 
ence to  figures  write  the  name  of  its  order  after  each  mammal :  — 
Ape  (Figs.  405,  406)         Cow  (Figs.  344,  386)         Antelope   (Fig.  391) 
Walrus  (Fig.  340) 
Monkey 

(Figs.  352,  401) 
Horse 

(Figs.  355,  395) 
Ant-eater 

(Figs.  354,  364) 


Rabbit  (Fig.  345) 
Dog  (Figs.  356.  408) 
Hog  (Figs.  357,  393) 
Bat  (Figs.  347,  370) 
Cat  (Figs.  337,  348) 
Armadillo 

(Figs.  349,  365) 


Mole 

(Figs.  367,  368) 
Beaver 

(Figs.  372.  373) 
Duckbill  (Fig.  359) 
Tapir  (Fig.  384) 
Dolphin  (379,  397) 


Use  chart  of  skulls  and  Figs.  381,  382,  395-400  in  working  out  this 
exercise. 

o 


(194) 


Chart  of  Mammalian  Skulls  (Illustrated  Study) 


Man's  dental  formula  is 


.1/  I 

5 


/  =32- 


In  like  manner  fill  out  formulas  below:  — 


Cow (A/—  C—  /— )2  =  32 

Rabbit (.1/—  C—  /-)2  =  28 

Walrus (M  —  C—  I— )*  =  34 

Bat (.1/—  C—  I—  )2  =  34 

Cat (M—  C—  /— )2  =  30 

Armadillo (;1/—  C—I-)*  =  28 

Horse (M —  C —  / — )2  =  40 


Whale ( M—  C—  I— )2  =    o 

Am.  Monkey. .  .(M—  C—  I—  )2  =  36 

Sloth (,!/—  C—  I—  )2  =  18 

Ant-eater (M—  C—  /— )2  =    o 

Dog (M—  C—  I—  )2  =  42 

Hog (A/-  C—  /— )2  =  44 

Sheep (M—  C—  /— )*  =  32 


Fig.  345.  —  Rabbit. 
^/,  ^,  incisors;   C,  molars. 


Fig.  348.  — Cat. 


Chart  of  Mammalian  Skulls 


(195) 


Fig.  349.  — Armadillo. 


Fig.  354.  —  Ant-eater  (Fig.  364). 


Fig.  353.  — Sloth  (Fig.  363) 


Fig.  358.  — Sheep. 


196 


ANIMAL    BIOLOGY 


The  lowest  order  of  mammals  contains  only  two  species, 
the   duckbill  and  the  porcupine   ant-eater,   both    living  in 

the  Australian  re- 
gion. Do  you  judge 
that  the  duckbill 
of  Tasmania  (Fig. 
359)  lives  chiefly  in 
water  or  on  land  ? 

Fig.  359.  —  Duckbill  (Ornithorhynchus  paradoxus).     vynv?      t„    :«.   DroK. 

ablv  active  or  slow  in  movement?  It  dabbles  in  mud  and 
slime  for  worms  and  mussels,  etc.  How  is  it  fitted  for 
doing  this  ?  Which 
feet  are  markedly, 
webbed  ?  How  far 
does  the  web  extend  ? 
The  web  can  be 
folded  back  when  not 
in  use.  It  lays  two 
eggs  in  a  nest  of 
grass  at  the  end  of  a 
burrow.  Trace  re- 
semblances and  dif- 
ferences between  this 
animal  and  birds. 

The  porcupine  ant- 
cater  has  numerous 
quill-like  spines  (Fig. 
360) interspersed  with 
its  hairs.  (Use  ?)  De- 
scribe its  claws.  It 
has  a  long  prehensile 
tongue.  It  rolls  into  a  ball  when  attacked.  Compare  its 
jaws  with  a  bird's  bill.     It  lays  one  egg,  which  is  carried 


Fig.  360.  —  Spiny  Ant-eater  (Echidna  acu- 
leata).  View  of  under  surface  to  show  pouch. 
(After  Haacke.) 


MAMMALS 


197 


in  a  fold  of  the  skin  until  hatched.  Since  it  is  pouched 
it  could  be  classed  with  the  pouched  mammals  (next  order), 
but  it  is  egg-laying.  Suppose  the  two  animals  in  this 
order  did  not  nourish  their  young  with  milk  after  hatching, 
would  they  most  resemble  mammals,  birds,  or  reptiles  ? 

Write   the   name    of   this    order.    (See   Table, 

p.   193.)      Why  do  you  place  them  in  this  order  ( )? 

See  p.  193.)    The  name  of  the  order  comes  from  two  Greek 


Fig.  361. 


OPOSSUM  (Didelphys  Virginicmus), 


words  meaning  "one  opening,"  because  the  ducts  from 
the  bladder  and  egg  glands  unite  with  the  large  intestine 
and  form  a  cloaca.  What  other  classes  of  vertebrates 
are  similar  in  this  ? 

Pouched  Mammals.  —  These  animals,  like  the  last,  are 
numerous  in  the  Australian  region,  but  are  also  found  in 
South  America,  thus  indicating  that  a  bridge  of  land  once 
connected  the  two  regions.  The  opossum  is  the  only 
species  which  has  penetrated  to  North  America  (Fig.  361). 
Are  its  jaws  slender  or  short  ?  What  kinship  is  thus  sug- 
gested ?     As  shown  by  its  grinning,  its  lips  are  not  well  de- 


198 


ANIMAL   BIOLOGY 


veloped.  Does  this  mean  a  low  or  a  well-developed  mam- 
mal ?  Where  does  it  have  a  thumb?  (Fig.  361.)  Does 
the  thumb  have  a  nail  ?  Is  the  tail  hairy  or  bare  ?  Why  ? 
Do  you  think  it  prefers  the  ground  or  the  trees  ?  State 
two  reasons  for  your  answer.  It  hides  in  a  cave  or  bank 
or  hollow  tree  all  clay,  and  seeks  food  at  night.  Can  it  run 
fast    on    the    ground  ?      It  feigns   death   when   captured, 

. ^a~>' ■  ■  — — — — ' — rr— —  anci  \\aicncs  ioi    a 

chance  for  stealthy 
escape. 

The  kangaroo 
(Fig.  362),  like  the 
opossum,  gives 
birth  to  imperfectly 
developed  young. 
(Kinship  with  what 
classes  is  thus  in- 
dicated?) After 
birth,  the  young 
( about  three  fourths 
of  an  inch  long) 
are  carried  in  a  ventral  pouch  and  suckled  for  seven  or 
eight  months.  They  begin  to  reach  down  and  nibble  grass 
before  leaving  the  pouch.  Compare  fore  legs  with  hind 
legs,  front  half  of  body  with  last  half.  Describe  tail. 
What  is  it  used  for  when  kangaroo  is  at  rest  ?  In  jump- 
ing, would  it  be  useful  for  propelling  and  also  for  balanc- 
ing the  body  ?    Describe  hind  and  fore  feet.     Order 

Why? See  key,  page  193. 

Imperfectly  Toothed  Mammals.  —  These  animals  live 
chiefly  in  South  America  (sloth,  armadillo,  giant  ant-eater) 
and  Africa  (pangolin).  The  sloth  (Fig.  363)  eats  leaves. 
Its  movements  are  remarkably  slow,  and  a  vegetable  growth 


Fig.  362.  —  Giant  Kangaroo. 


MAMMALS 


199 


Fig   363.  —  Sloth  of  South  America. 


resembling  moss  often  gives  its  hair  a  green  color.  (What 
advantage?)  How  many  toes  has  it?  How  are  its  nails 
suited  to  its  man- 
ner of  living?  Does 
it  save  exertion  by 
hanging  from  the 
branches  of  trees 
instead  of  walking 
upon  them  ? 

Judging  from  the 
figures  (363,  364, 
365),  are  the  mem- 
bers of  this  order 
better  suited  for  at- 
tack, active  resistance,  passive  resistance,  or  concealment 

when  contend- 
ing with  other 
animals  ?  The 
ant-eater's  claws 
J|  (Fig.  364) on  the 
fore  feet  seem 
to  be  a  hin- 
drance in  walk- 
ing ;  for  what 
are  they  useful  ? 
Why  are  its  jaws 
so  slender? 
What  is  prob- 
ably the  use  of 
the  enormous 
bushy  tail  ?  The 
nine-banded  armadillo  (Fig.  365)  lives  in  Mexico  and  Texas. 
It  is  omnivorous.     To  escape  its  enemies,  it  burrows  into 


'iL*j'*L  '"W't-JTSs, 


Fig.  364.  —  Giant  Ant-eater  of  South  America. 
(See  Fig.  354. )  Find  evidences  that  the  edentates  are  a 
degenerate  order.  Describe  another  ant-eater  (Fig.  360). 


200 


ANIMAL   BIOLOGY 


the  ground  with  surprising  rapidity.     If  unable  to  escape 
when   pursued,   its  hard,   stout  tail   and   head  are   turned 

under  to  protect 
the  lower  side  of 
the  body  where 
there  are  no  scales. 
The  three-banded 
species  (Fig.  366) 

lives  in  Argentina. 

Fig.   365.  —  Nine-banded    Armadillo   of  Texas      ^  ,, 

,..  ,     .    ...  .  Compare  the  ears 

and  Mexico.    \Dasypus  novemctnetus.)    It  is  mcreas-  : 

ing  in  numbers;   it  is  very  useful,  as  it  digs  up  and       and  tail  of  the  two 

destroys  insects.      (See  Fig.  347.) 

'  species  ;  give  rea- 
sons for  differences.  Why  are  the  eyes  so  small?  The 
claws  so  large  ?      Order Why? 


Fig.  366.  —  Three-banded  Armadillo  {Tolypeutes  tricinctus) . 

Insect  Eaters.  — The  soft  interior  and  crusty  covering  of 
insects  makes  it  unnecessary  for  animals  that  prey  upon 
them    to    have    flat-topped    teeth    for    grinding    them    to 


MAMMALS 


20I 


powder,  or  long  cusps  for  tearing  them  to  pieces.  The 
teeth  of  insect  eaters,  even  the  molars  (Fig.  368),  have 
many  sharp  tubercles,  or  points,  for  holding  insects  and 
piercing  the  crusty  outer  skeleton  and  reducing  it  to  bits. 
As  most  insects  dig  in  the  ground  or  fly  in  the  air,  we 
are  not  surprised  to  learn  that  some  insect-eating  mam- 


Fig.  367. —The  Mole. 


mals  (the  bats)  fly  and   others  (the  moles)  burrow.     Are 
the  members  of  this  order  friends  or  competitors  of  man  ? 


FlG.  368.  —  Skeleton  of  Moll.     (Shoulder  blade  is  turned  upward.) 

Why  does  the  mole  have  very  small  eyes  ?  Small  ears  ? 
Compare  the  shape  of  the  body  of  a  mole  and  a  rat. 
What  difference  ?  Why  ?  Compare  the  front  and  the  hind 
legs  of  a  mole.  Why  are  the  hind  legs  so  small  and 
weak?  Bearing  in  mind  that  the  body  must  be  arranged 
for  digging  and  using  narrow  tunnels,  study  the  skeleton 


202  ANIMAL   BIOLOGY 

(Fig.  368)  in  respect  to  the  following:  Bones  of  arm 
(length  and  shape),  fingers,  claws,  shoulder  bones,  breast- 
bone (why  with  ridge  like  a  bird  ?),  vertebrae  (why  are  the 
first  two  so  large?),  skull  (shape).  There  are  no  eye 
sockets,  but  there  is  a  snout  gristle  ;  for  the  long,  sensitive 
snout  must  serve  in  place  of  the  small  and  almost  useless 
eyes  hidden  deep  in  the  fur.  Is  the  fur  sleek  or  rough  ? 
Why  ?  Close  or  thin  ?  It  serves  to  keep  the  mole  clean. 
The  muscles  of  neck,  breast,  and  shoulders  are  very 
strong.  Why  ?  The  mole  eats  earthworms  as  well  as 
insects.  It  injures  plants  by  breaking  and  drying  out 
their  roots.  Experiments  show  that  the  Western  mole  will 
eat  moist  grain,  though  it  prefers  insects.  If  a  mole  is 
caught,  repeat  the  experiment,  making  a  careful  record  of 
the  food  placed  within  its  reach. 


di  c     «    r     '»'    cl 


Fig.  369. —  Skeleton  of  Bat. 

As  with  the  mole,  the  skeletal  adaptations  of  the  bat 
are  most  remarkable  in  the  hand.  How  many  fingers  ? 
(Fig.  369.)  How  many  nails  on  the  hand  ?  Use  of 
nail  when  at  rest?  When  creeping?  (Fig.  369.)  In- 
stead of  feathers,  the  flying  organs  are  made  of  a  pair 
of  extended  folds  of  the  skin  supported  by  elongated 
bones,  which  form  a  framework  like  the  ribs  of  an  um- 
brella or  a  fan.     How  many  digits  are  prolonged  ?     Does 


MAMMALS 


203 


OP 


£?%£       '""S 


Fig.  370.  —VAMPIRE  {Phyllostoma.  spectrum)  of  South  America.     X  \. 

the  fold  of  the  skin  extend  to  the  hind  legs  ?  The  tail  ? 
Are  the  finger  bones  or  the  palm  bones  more  prolonged 
to  form  the  wing  skeleton  ? 

The  skin  of  the  wing  is  rich  in  blood  vessels  and  nerves, 
and  serves,  by  its  sensitiveness  to  the  slightest  current  of 
air,  to  guide  the  bat  in  the  thickest  darkness.  Would  you 
judge  that  the  bat  has  sharp  sight  ?     Acute  hearing? 

The  moles  do  not  hibernate ;  the  bats  do.  Give  the 
reason  for  the  difference.  If  bats  are  aroused  out  of  a 
trance-like  condition  in  winter,  they  may  die  of  starvation. 
Why  ?  The  mother  bat  carries  the  young  about  with  her, 
since,  unlike  birds,  she  has  no  nest.  How  are  the  young 
nourished  ?     Order Why  ? (Key,  p.  193.) 

The  Gnawing  Mammals.  — These  animals  form  the  most 
numerous  order  of  mammals.  They  lack  canine  teeth.  In- 
ference ?     The  incisors  are  four  in  number  in  all  species 


204 


ANIMAL   BIOLOGY 


except  the  rabbits,  which  have  six  (see  Fig.  345).  They 
are  readily  recognized  by  their  large  incisors.  These  teeth 
grow  throughout  life,  and  if  they  are  not  constantly  worn 


Fig.  371.  —  Pouched  Gopher  {Geomys  bursarius)  xj,a  large,  burrowing 
field  rat,  with  cheek  pouches  for  carrying  grain. 

away  by  gnawing  upon  hard  food,  they  become  incon- 
veniently long,  and  may  prevent  closing  of  the  mouth  and 
cause  starvation.  The  hard  enamel  is  all  on  the  front  sur- 
face, the  dentine  in  the  rear  being  softer  ;  hence  the  in- 
cisors  sharpen  themselves  by  use   to   a  chisel-like  edge. 


Fig.  372. —  Hind  foot  a,  fore  foot  b, 
tail  c,  of  Beaver. 


Fig.  373.  — Beaver. 


The  molars  are  set  close  together  and  have  their  upper 
surfaces  level  with  each  other.  The  ridges  on  them  run 
crosswise  so  as  to  form  a   continuous  filelike  surface  for 


MAMMALS 


205 


reducing  the  food  still  finer  after  it  has  been  gnawed  off 
(Fig.  345).  The  lower  jaw  fits  into  grooves  in  place  of 
sockets.  This  allows  the  jaw  to  work  back  and  forth  in- 
stead of  sidewise.  The  rabbits  and  some  squirrels  have  a 
hare  lip ;  i.e.  the  upper  lip  is  split.  What  advantage  is 
this  in  eating  ?  In  England  the  species  that  burrow  are 
called  rabbits ;  those  that  do  not  are  called  hares. 

Name  six  enemies  of  rabbits.  Why  does  a  rabbit  usually 
sit  motionless  unless  approached  very  close  ?  Do  you 
usually  see  one  before  it  dashes  off?  A  rabbit  has  from 
three  to  five  litters  of  from  three  to  six  young  each  year. 
Squirrels  have  fewer  and  smaller 
litters.  Why  must  the  rabbit 
multiply  more  rapidly  than  the 
squirrel  in  order  to  survive  ? 
English  rabbits  have  increased 
in  Australia  until  they  are  a 
plague.  Sheep  raising  is  inter- 
fered with  by  the  loss  of  grass. 
The  Australians  now  ship  them  to  England  in  cold  storage 
for  food.  Rabbits  and  most  rodents  lead  a  watchful, 
timid,  and  alert  life.  An  exception  is  the  porcupine, 
which,  because  of  the  defense  of  its  barbed  quills,  is  dull 
and  sluggish. 

The  common  rodents  are  :  — 


Fig.  374.  — Position  of  Limbs 
in  Rabbit. 


pouched  gopher 
prairie   dog 
prairie  squirrel 
chipmunk 


ground    hog 
field   mouse 


squirrels  beavers 

rabbits  muskrats 

rats  porcupines 

mice  guinea  pig 

Which  of  the  above  rodents  are  commercially  important  ? 
Which  are  injurious  to  an  important  degree  ?  Which  have 
long  tails  ?    Why  ?    Short  tails?    Why  ?    Long  ears  ?  Why  ? 


206 


ANIMAL  BIOLOGY 


Short  ears  ?  Why  ?  Which  are  aquatic  ?  Which  dig  or  bur- 
row ?  Which  are  largely  nocturnal  in  habits?  Which  are 
arboreal  ?  Which  are  protected  by  coloration  ?  Which 
escape  by  running  ?     By  seeking  holes  ? 

Economic  Importance.  —  Rabbits  and  squirrels  destroy  the 
eggs  and  young  of  birds.  Are  rabbits  useful  ?  Do  they 
destroy  useful  food  ?  The  use  of  beaver  and  muskrat  skins 
as  furs  will  probably  soon  lead  to  their  extinction.  Millions 
of  rabbits'  skins  are  used  annually,  the  hair  being  made  into 


Fir,.  375.  —  Flying  Squirrel  (Pteromys volucelld) .     -■  '.,. 

felt  hats.  There  are  also  millions  of  squirrel  skins  used 
in  the  fur  trade.  The  hairs  of  the  tail  are  made  into  fine 
paint  brushes.     The  skins  of  common  rats  are  used  for  the 

thumbs  of  kid  gloves.      Order Why? 

Elephants.  —  Elephants,  strange  to  say,  have  several 
noteworthy  resemblances  to  rodents.  Like  them,  elephants 
have  no  canine  teeth  ;  their  molar  teeth  are  few,  and  marked 
by  transverse  ridges  and  the  incisors  present  are  promi- 
nently developed  (Figs.  376,  377).  Instead  of  four  incisors, 
however,  they  have  only  two,  the  enormous  tusks,  for  there 
are  no  incisors  in  the  lower  jaw.       Elephants  and  rodents 


MAMMALS 


207 


Fig.  376.  —  Head  of  African  Elephant. 


both  subsist  upon  plant  food.  Both  have  peaceful  disposi- 
tions, but  one  order  has  found  safety  and  ability  to  survive 
by  attaining  enormous  size  and  strength  ;  the  other  {e.g. 
rats,  squirrels)  has  found  safety  in  small  size.     Explain. 

Suppose  you  were 
to  observe  an  elephant 
for  the  first  time,  with- 
out knowing  any  of  its 
habits.  How  would 
you  know  that  it  does 
not  eat  meat  ?  That  it 
does  eat  plant  food  ? 
That  it  can  defend  it- 
self ?  Why  would  you  make  the  mistake  of  thinking  that 
it  is  very  clumsy  and  stupid  ?  Why  is  its  skin  naked  ? 
Thick  ?  Why  must  its  legs  be  so  straight  ?  Why  must  it 
have  either  a  very  long  neck  or  a  substitute  for  one? 
(Fig.  376.)  Are  the  eyes  large  or  small?  The  ears?  The 
brain  cavity  ?  What  anatomical  feature  correlates  with 
the  long  proboscis?  Is  the  proboscis  a  new  organ  not 
found  in  other  animals,  or  is  it  a  specialization  of  one  or 
more  old  ones  ?  Reasons  ?  What  senses  are  especially 
active  in  the  proboscis  ?      How  is  it  used  in  drinking  ?     In 

grasping  ?  What  evidence  that 
it  is  a  development  of  the 
nose  ?     The  upper  lip  ? 

The  tusks  are  of  use  in  up- 
rooting trees  for  their  foliage 
and  in  digging  soft  roots  for 
food.  Can  the  elephant  graze  ?  Why,  or  why  not  ?  There 
is  a  finger-like  projection  on  the  end  of  the  snout  which  is 
useful  in  delicate  manipulations.  The  feet  have  pads  to 
prevent  jarring;  the  nails  are  short  and  hardly  touch  the 
ground.     Order Why? Key,  page  193. 


Fig.   377.  — Molar    Tooth    of 
African  Elephant. 


208 


ANIMAL   BIOLOGY 


Whales,  Porpoises,  Dolphins.  —  As  the  absurd  mistake 
is  sometimes  made  of  confusing  whales  with  fish,  the  pupil 
may  compare  them  in  the  following  respects  :  eggs,  nour- 
ishment of  young,  fins,  skin,  eyes,  size,  breathing,  tem- 
perature, skeleton  (Figs.  209,  379,  and  397). 


H&T- 


Fig.  378. —  Harpooning  Greenland  Whale 
(see  Fig.  351). 

Porpoises  and  dolphins,  which  are  smaller  species  of 
whales,  live  near  the  shore  and  eat  fish.  Explain  the  ex- 
pression "  blow  like  a  porpoise."  They  do  not  exceed  five 
or  eight  feet  in  length,  while  the  deep-sea  whales  are  from 
thirty  to  seventy-five  feet  in  length,  being  by  far  the  largest 
animals  in  the  world.  The  size  of  the  elephant  is  limited 
by  the  \peight  that  the  bones  and  muscles  support  and 
move.     The  whale's  size  is  not  so  limited. 

The  whale  bears  one  young  (rarely  twins)  at  a  time. 
The  mother  carefully  attends  the  young  for  a  long  time. 
The  blubber,  or  thick  layer  of  fat  beneath  the  skin,  serves 
to  retain  heat  and  keep  the  body  up  to  the  usual  tempera- 
ture of  mammals  in  spite  of  the  cold  water.  It  also  serves, 
along  with  the  immense  lung's,  to  give  lightness  to  the  body. 


MAMMALS 


209 


Why  does  a  whale  need  large  lungs  ?     The  tail  of  a  whale 

is  horizontal  instead 
of  vertical,  that  it  may 
steer  upward  rapidly 
from  the  depths  when 
needing  to  breathe. 
The  teeth  of  some 
fig.  379. -dolphin.  whales  do  not  cut  the 

gum,  but  are  reabsorbed  and  are  replaced  by  horny  plates 
of  "whalebone,"  which  act  as  strainers.  Give  evidence, 
from  the  flippers,  lungs,  and  other  organs,  that  the  whale 
is  descended  from  a  land  mammal  (Fig.  397).  Compare 
the  whale  with  a  typical  land  mammal,  as  the  dog,  and 
enumerate  the  specializations  of  the  whale  for  living  in 
water.  What  change  took  place  in  the  general  form  of  the 
body  ?  It  is  believed  that  on  account  of  scarcity  of  food 
the  land  ancestors  of  the  whale,  hundreds  of  thousands  of 
years  ago,  took  to  living  upon  fish,  etc.,  and,  gradually  be- 
coming swimmers  and  divers,  lost  the  power  of  locomotion 
on  land.      Order Why  ? 

Elephants  are  rapidly  becoming  extinct  because  of  the 
value  of  their 

ivory     tusks.  IKS  .^tfn^^l 

Whales  also 
furnish  valua- 
ble products, 
but  they  will 
probably  exist 
much  longer. 
Why  ? 

The  manatees  and  dugongs  (sea  cows)  are  a  closely  re- 
lated order  living  upon  water  plants,  and  hence  living  close 
to  shore  and  in  the  mouths  of  rivers.     Order Why  ? 


Fig.  380.  —  Manatee,  or  sea  cow ;  it  lives  near  the  shore 
and  eats  seaweed.     (Florida  to  Brazil.) 


2IO 


ANIMAL   BIOLOGY 


Hoofed  Mammals. — All  the  animals  in  this  order  walk 
on  the  tips  of  their  toes,  which  have  been  adapted  to  this 
use  by  the  claws  having  developed  into  hoofs.  The  order 
is  subdivided  into  the  odd-toed  (such  as  the  horse  with  one 
toe  and  the  rhinoceros  with  three)  and  the  even-toed  (as 
the  ox  with  two  toes  and  the  pig  with  four).  All  the  even- 
toed  forms  except  the  pig  and  hippopotamus  chew  the  cud 
and  are  given  the  name  of  ruminants. 

Horse  and  Man  Compared  (Figs.  381,  399).  —  To  which 
finger  and  toe  on  man's  hand  and  foot  does  the  toe  of  a 

horse's  foot  correspond  ? 
Has  the  horse  kneecaps  ? 
Is  its  heel  bone  large  or 
small  ?  Is  the  fetlock  on 
toe,  instep,  or  ankle  ? 
Does  the  part  of  a  horse's 
hind  leg  that  is  most  elon- 
gated correspond  to  the 
thigh,  calf,  or  foot  in 
man  ?  On  the  fore  leg, 
is  the  elongated  part  the 
upper  arm,  forearm,  or 
hand  ?  Does  the  most 
elongated  part  of  the  fore 
foot  correspond  to  the  finger,  palm,  or  wrist  ?  On  the  hind 
coot  is  it  toe,  instep,  or  ankle?  Is  the  fetlock  at  the  toe, 
instep,  or  heel  ?  (Fig.  385.)  Is  the  hock  at  the  toe,  in- 
step, heel,  or  knee  ?     Order Why  ? 

Specializations  of  the  Mammals.  —  The  early  mammals, 
of  which  the  present  marsupials  are  believed  to  be  typical, 
had  five  toes  provided  with  claws.  They  were  not  very 
rapid  in  motion  nor  dangerous  in  fight,  and  probably  ate 
both  animal  and  vegetable  food. 


Fig.  381.  —  Left  leg  of  man,  left  hind  leg 
of  dog  and  horse ;  homologous  parts 
lettered  alike. 


MAMMALS 


211 


Fig.  382. —  Skeletons  of  Feet  of  Mammals. 

P,  horse;   D,  dolphin;   E,  elephant;  A,  monkey;   T,  tiger;   O,  aurochs:  Miohippus 

F,  sloth;  M,  mole. 

Question:     Explain  how  each  is  adapted  to  its  specialized  function. 

According  to  the  usual  rule,  they  tended  to 
increase  faster  than  the  food  supply,  and  there 
were  continual  contests  for  food.  Those  whose 
claws  and  teeth  were  sharper  drove  the  others 
from  the  food,  or  preyed  upon  them.  Thus  the 
specialization  into  the  bold  flesh  eating  beasts 
of  prey  and  the  timid  vegetable  feeders  began. 
Which  of  the  flesh  eaters  has  already  been  stud- 
ied at  length  ?  The  insectivora  escaped  their 
enemies  and  found  food  by  learning  to  burrow 
or  fly.  The  rodents  accomplished  the  same  result  either  by 
acquiring  great  agility  in  climbing,  or  by  living  in  holes,  or 
by  running.  The  proboscidians  acquired  enormous  size 
and  strength.    The  hoofed  animals  found  safety  in  flight. 


Oroltippus. 

Fig.  383.— 
Feet  of  the 

ancestors  of 
the  horse. 


212 


ANIMAL   BIOLOGY 


■ 


Fig.  384.  —  Tapir  of  south  America  (  Tapirus  a?nericanus).  x  5V 

Questions:    How  does  it  resemble  an  elephant?    (Fig.  376.)     A  horse  ?  (p.  210.) 

Ungulates,  as  the  horse,  need  no  other  protection  than 
their  great  speed,  which  is  due  to  lengthening  the  bones  of 

the  legs  and  rising 
upon  the  very  tip  of 
the  largest  toe,  which, 
to  support  the  weight, 
developed  an  enor- 
mous toe-nail  called  a 
hoof.  The  cattle,  not 
having  developed  such 
speed  as  the  horse, 
usually  have  horns 
for  defense.  If  a  calf 
or  cow  bellows  with  distress,  all  the  cattle  in  the  neigh- 
borhood rush  to  the  rescue.  This  unselfish  instinct  to 
help  others  was  an  aid  to  the  survival  of  wild  cattle  living 
in  regions  infested  with  beasts  of  prey.  Which  of  vEsop's 
fables  is  based  upon  this  instinct  ?  The  habit  of  rapid 
grazing  and  the  correlated  habit  of  chewing  the  cud  were 
also  of  great  value,  as  it  enabled  cattle  to  obtain  grass  hur- 


Fig.  385.  —  Horse,  descended  from  a  smal 
wild  species  still  found  in  Western  Asia. 


MAMMALS 


213 


FIG.  386.  —  Skeleton'  of  Cow.     Compare  with  horse 
(Fig.  395)  as  to  legs,  toes,  tail,  mane,  dewlap,  ears,  body. 


riedly  and  retire  to  a  safe  place  to  chew  it.  Rudiments  of 
the  upper  incisors  are  present  in  the  jaw  of  the  calf,  show- 
ing the  descent  from  animals  which  had  a  complete  set  of 
teeth.  The  rudiments  are  absorbed  and  the  upper  jaw  of 
the  cow  lacks  incisors  entirely,  as  they  would  be  useless 
because  of  the  cow's  habit  of  seizing  the  grass  with  her 
rough  tongue 
and  cutting  it 
with  the  lower 
incisors  as  the 
head  is  jerked 
forward.  This 
is  a  more  rapid 
way  of  eating 
than  by  biting. 
Which  leaves 
the  grass  shorter 

after  grazing,  a  cow  or  a  horse  ?  Why  ?  Grass  is  very 
slow  of  digestion,  and  the  ungulates  have  an  alimentary 
canal  twenty  to  thirty  times  the  length  of  the  body. 
Thorough  chewing  is  necessary  for  such  coarse  food,  and 
the  ungulates  which  chew  the  cud  (ruminants)  are  able, 
by  leisurely  and  thorough  chewing,  to  make  the  best  use 
of  the  woody  fiber  (cellulose)  which  is  the  chief  substance 
in  their  food. 

Ruminants  have  four  divisions  to  the  stomach.  Their 
food  is  first  swallowed  into  the  roomy  paitncJi  in  which, 
as  in  the  crop  of  a  bird,  the  bulky  food  is  temporarily 
stored.  It  is  not  digested  at  all  in  the  paunch,  but  after 
being  moistened,  portions  of  it  pass  successively  into  the 
honeycomb,  which  forms  it  into  balls  to  be  belched  up  and 
ground  by  the  large  molars  as  the  animal  lies  with  eyes 
half  closed  under  the  shade  of  a  tree.     It  is  then   swal- 


214 


ANIMAL   BIOLOGY 


lowed  a  second  time  and  is  acted  upon  in  the  third  divi- 
sion ( or  manyplies)  and  the  fourth  division  (or  reed ).     Next 


_$7. —  Food  traced 
through  stomachs  of 
cow.   (Follow  arrows.) 


Fig.  3S8.  — Section  of  cow's  stomachs. 
Identify  each.      (See  text.) 


it  passes  into  the  intestine.  Why  is  the  paunch  the  largest 
compartment  ?  In  the  figure  do  you  recognize  the  paunch 
by  its    size  ?     The  honeycomb  by  its  lining  ?     Why  is  it 

round  ?  The  last  two 
of  the  four  divisions 
may  be  known  by  their 
direct  connection  with 
the  intestine. 

The  true  gastric  juice 
is  secreted  only  in  the 
fourth  stomach.  Since 
the  cud  or  unchewed 
food  is  belched  up  in 
balls  from  the  round 
"  honeycomb,"  and  since 
a  ball  of  hair  is  some- 
times found  in  the  stom- 
ach of  ruminants,  some 
ignorant  people  make  the  absurd  mistake  of  calling  the 
ball  of  hair  the  cud.     This  ball  accumulates  in  the  paunch 


Fig.  389.  —  OKAPI.  This  will  probably  prove 
to  be  the  last  large  mammal  to  be  discovered 
by  civilized  man.  It  was  found  in  the  for- 
ests of  the  Kongo  in  1900. 

Questions:  It  shows  affinities  (find  them)  with 
giraffe,  deer,  and  zebra.  It  is  a  ruminant  ungulate 
(explain  meaning  —  see  text). 


MAMMALS 


215 


because  of  the  friendly  custom  cows  have  of  combing  each 
other's  hair  with  their  rough  tongues,  the  hair  sometimes 


Fig.  390.  —  African  Camel  (Camelus  dromedarius) . 

being  swallowed.     Explain  the  saying  that  if  a  cow  stops 
chewing  the  cud  she  will  die. 

Does    a    cow's  lower  jaw  move  sidewise  or 
back  and  forth  ?     Do  the  ridges  on  the  molars 
run  sidewise  or  lengthwise?     Is' a 
cow's    horn    hollow  ?      Does  it 
have  a  bony  core  ?    (Fig.  344.) 

The  permanent  hol- 
low horns  of  the  cow 
and  the  solid  decidu- 
ous horns  of  the  deer 
are  typical  of  the  two 
kinds  of  horns  pos- 
sessed by   ruminants. 

The  prong-horned  an- 

r        °  Fig.  391.  — Prong-horned  Antelope 

telope     (Fig.     391)     Of  {Antelocarpa  Americana) .     Western  states. 


2l6 


AXIMAL    BIOLOGY 


the  United  States,  however,  is  an  intermediate  form,  as  its 
horns  are  hollow,  but  are  she'd  each  year.  The  hollow 
horns  are  a  modification  of  hair.  Do  solid  or  hollow 
bones  branch  ?  Which  are  possessed  by  both  sexes  ? 
Which  are  pointed  ?  Which  are  better  suited  for  fight- 
ing ?  Why  would  the  deer  have  less  need  to  fight  than 
the  cattle  ?     Deer  are  polygamous,  and  the  males  use  their 


Fig.  392.  —  Rocky  Mountain  Sheep  (Ovis  montcmd) .     x?\. 

horns  mostly  for  fighting  each  other.  The  sharp  hoofs  of 
deer  are  also  dangerous  weapons.  The  white-tail  deer 
(probably  the  same  species  as  the  Virginian  red  deer)  is 
the  most  widely  distributed  of  the  American  deer.  It 
keeps  to  the  lowlands,  while  the  black-tailed  deer  prefers 
a  hilly  country.  The  moose,  like  the  deer,  browses  on 
twigs  and  leaves.     The  elk,  like  cattle,  eats  grass. 

The  native  sheep  of  America  is  the  big  horn,  or  Rocky 
Mountain  sheep  (Fig.  392).     The  belief  is  false  that  they 


MAMMALS 


2iy 


alight  upon  their  horns  when  jumping  down  precipices. 
They  post  sentinels  and  are  very  wary.  There  is  also  a 
native  goat,  a  white  species,  living  high  on  the  Rocky 
Mountains  near  the  snow.  They  are  rather  stupid  ani- 
mals. The  bison  once  roamed  in  herds  of  countless  thou- 
sands, but,  with  the  exception  of  a  few  protected  in  parks, 
it  is  now  extinct.  Its  shaggy  hide  was  useful  to  man  in 
winter,  so  it  has  been  well-nigh  destroyed.  For  gain  man 
is  led  to  exterminate  elephants,  seals,  rodents,  armadillos, 
whales,  birds,  deer,  mussels,  lobsters,  forests,  etc. 


Fig.  393.  —  Peccary  {Dicotyles  torquatus)  of  Texas  and  Mexico,     x  ^. 

Our  only  native  hog  is  the  peccary,  found  in  Texas  (Fig. 
393).  In  contrast  with  the  heavy  domestic  hog,  it  is 
slender  and  active.  It  is  fearless,  and  its  great  tusks  are 
dangerous  weapons.  The  swine  are  the  only  ungulates 
that  are  not  strictly  vegetable  feeders.  The  habit  of  fat- 
tening in  summer  was  useful  to  wild  hogs,  since  snow  hid 
most  of  their  food  in  winter.  The  habit  has  been  pre- 
served under  domestication.  Are  the  small  toes  of  the 
hog  useless?  Are  the  "dew  claws"  of  cattle  useless? 
Will  they  probably  become  larger  or  smaller  ?      Order  ? 


218 


Illustrated  Study 


Illustrated  Study 


219 


Fig.  400.  —  Chimpanzee.     (See  Fig.  406.) 

Illustrated  Study  of  Vertebrate  Skeletons : 
Taking  man's  skeleton  as  complete,  which  of  these 
seven  skeletons  is  most  incomplete  ? 

Regarding  the  fish  skeleton  as  the  original  verte- 
brate skeleton,  how  has  it  been  modified  for 
(1)  walking,  (2)  walking  on  two  legs,  (3)  flying  ? 

Which  skeleton  is  probably  a  degenerate  reversion 
to  original  type  ?  (p.  209.) 

How  is  the  horse  specialized  for  speed  ? 

Do  all   have   tail  vertebras,  or  vertebrae   beyond 

►  the  hip  bones  ?       Does  each  have  shoulder  blades  ? 

Compare  (1)  fore  limbs,  (2)  hind  limbs,  (3)  jaws 

of  the  seven  skeletons.     Which   has  relatively   the 

FIG.  39a. MAN.  shortest  jaws?     Why?     What    seems    to    be    the 

typical  number  of  ribs  ?  limbs  ?  digits  ?     • 
Does  flipper  of  a  dolphin  have  same  bones  as  arm  of  a  man  ? 
How  many  thumbs  has  chimpanzee  ?     Which  is  more  specialized,  the  foot  of  a 
man  or  a  chimpanzee?     Is  the  foot  of  a  man  or  a  chimpanzee  better  suited  for 
supporting  weight  ?     How  does  its  construction  fit  it  for  this  ? 

Which  has  a  better  hand,  a  man  or  a  chimpanzee  ?     What  is  the  difference  in 
their  arms  ?     Does  difference  in  structure  correspond  to  difference  in  use  ? 
Which  of  the  seven  skeletons  bears  the  most  complex  breastbone  ? 
Which  skeleton  bears  no  neck  (or  cervical)  vertebrae  ?     Which  bears  only  one  ? 
Are  all  the  classes  of  vertebrates  represented  in  this  chart  ?   (p.  125.) 


220 


A  XI  MA  I.    BIOLOGY 


Fig.  401.  — Sacred  Monkey  of  India  {Semnopithecus  entellus).    x  & 

Monkeys,  Apes,  and  Man. — 

Study  the  figures  (399,  400); 
compare  apes  and  man  and  ex- 
plain each  of  the  differences  in 
the  following  list :  ( 1 )  feet,  three 
differences;  (2) arms;  (3) brain 
case;  (4)  jaws;  (5)  canine 
teeth  ;  (6)  backbone  ;  (7)  dis- 
tance between  the  eyes. 

A  hand,  unlike  a  foot,  has 
one  of  the  digits,  called  a 
thumb,  placed  opposite  the 
other  four  digits  that  it  may  be 
used  in  grasping.  Two-handed 
man  and  four-handed  apes  and 
monkeys  are  usually  placed  in        Fig.  402. -Lemur  (Z« 

goz).     X  ia.      Which  digit  bears  a 

one    order,    the    Primates,    or     ciaw? 


MAMMALS 


221 


in  two  orders  (see  table,  page  193).     The  lowest  members 
of  this  order  are  the  lemurs  of  the  old  world.     Because  of 


ft 


1  WiW 


Fig.  403.  —  Broad-nosed 
Monkey,     x  tV    America. 


Fig.  404.  —  Narrow-nosed 
Monkey.      X  -n-    Old  World. 


their  hands  and  feet  being  true  grasping  organs,  they  are 
placed  among  the  primates,  notwithstanding  the  long 
muzzle  and  expres- 
sionless, foxlike  face. 
(Fig.  402.)  Next  in 
order  are  the  tailed 
monkeys,  while  the 
tailless  apes  are  the 
highest  next  to  man. 
The  primates  of  the 
Nezv  World  are  all 
monkeys  with  long 
tails  and  broad  noses. 
They  are  found  from 
Paraguay  to  Mexico. 
The  monkeys  and  apes 
of  the  Old  IVorldhave 
a  thin  partition  be- 
tween the  nostrils, 
and  are  thus  distin- 
guished     from      the 


FlG.  405.  —  Gorilla.     (Size  of  a  man.) 


ANIMAL    BIOLOGY 


monkeys  of  the  New  World,  which  have  a  thicker  par- 
tition and  have  a  broader  nose.  (Figs.  403,  404.)  The 
monkeys  of  America  all  have  six  molar  teeth  in  each  half 
jaw  (Fig.  352);  the  monkeys  and  apes  of  the  Old  World 
have  thirty-two  teeth  which  agree  both  in  number  and 
arrangement  with  those  of  man. 

Which  of  the  primates  figured  in  this  book  appear  to 
have   the  arm    longer   than    the   leg  ?      Which    have   the 

eyes  directed  forward  instead  of 
sideways,  as  with  cats  or  dogs  ? 
Nearly  all  the  primates  are 
forest  dzvellers,  and  inhabit  warm 
countries,  where  the  boughs  of 
trees  are  never  covered  with  ice 
or  snow.  Their  ability  in  climb- 
ing serves  greatly  to  protect 
them  from  beasts  of  prey. 
Many  apes  and  monkeys  are 
able  to  assume  the  upright  posi- 
tion in  walking,  but  they  touch 
the  ground  with  their  knuckles 
every  few  steps  to  aid  in  preserving  the  balance. 

The  Simians  are  the  highest  family  of  primates  below 
man,  and  include  the  gorilla,  chimpanzee,  orang,  and  gib- 
bon. Some  of  the  simians  weave  together  branches  in  the 
treetops  to  form  a  rude  nest,  and  all  are  very  affectionate 
and  devoted  to  their  young.  How  are  apes  most  readily 
distinguished  from  monkeys?     (Figs.  401,  406.) 

The  study  of  man  as  related  to  his  environment  will  be 
taken  up  in  detail  in  the  part  called  Human  Biology.  We 
will  there  examine  the  effect  upon  man's  body  of  the  rapid 
changes  since  emerging  from  savagery  that  he  has  made 
in  food  eaten,  air  breathed,  clothing,  and  habits  of  life. 


Fig.  406.  —  Chimpanzee. 


MAMMALS 


223 


Fig.  407.  —  Anatomy  of  Rabbit, 


a,  incisor  teeth; 

b,  b' ,  b" ,  salivary 
glands : 

k,  larynx; 
I,  windpipe; 

c,  gullet; 

d,  diaphragm 
(possessed  only 
by  mammals) ; 

e,  stomach; 

g,  small  intestine; 

h,  h' ,  large  intes- 
tine; 
y,   junction  of  small 
and  large  intes- 
tine; 

g,  g' ,  caecum,  or 
blind  sac  fromy 
(corresponds   to 


rudiment  ary 
vermiform  ap- 
pendix in  man); 

m,  carotid  arte- 
ries ; 

«,  heart; 

o,  aorta; 

p>  lungs; 

q,  end  of  sternum; 

r,  spleen; 

s,  kidney; 

t,  ureters  (from 
kidney  to  blad- 
der v). 

2    brain  of  rabbit: 

a,  olfactory 
nerves; 

b,  cerebrum: 

c,  midbrain; 


the      shrunken     d,  cerebellum. 


Table  for  Review 


Fish 

Frog 

Turtle 

Bird 

Cat 

Horse 

Man 

Names  of  limbs 

Acutest  sense 

Digits    on   fore 
and  hind  limb 

Locomotion 

Kind  of  food 

Care  of  young 

Pointer         Newfoundland 
Bulldog  Shepherd 

Greyhound  Spitz 


Fig.  408.  —  Artificial  Selection.  Its  effects  in  causing  varieties  in  one  species. 
Which  of  the  dogs  is  specialized  for  speed  ?  Driving  cattle  ?  Stopping  cattle  ? 
Trailing  by  scent  ?  Finding  game  ?  Drawing  vehicles  ?  Going  into  holes  ? 
House  pet  ?  Cold  weather  ?  In  Mexico  there  is  a  hairless  dog  specialized  for  hot 
climates.  The  widely  differing  environments  under  various  forms  of  domestica- 
tion cause  "  sports  "  which  breeders  are  quick  to  take  advantage  of  when  wishing 
to  develop  new  varieties.  Professor  De  Vries  by  cultivating  American  evening 
primroses  in  Europe  has  shown  that  a  sudden  change  of  environment  may  cause 
not  only  varieties  but  new  species  to  arise. 


224 


HUMAN    BIOLOGY 


CHAPTER  I 


INTRODUCTION 

To  which  branch  of  animals  does  man  belong  ?  To 
which  class  and  order  in  that  branch  ?  (Animal  Biology, 
pages  125,  193.)  There  is  no  other  animal  species  in  the 
same  genus  or  order  with  man.  This  shows  a  wide  physi- 
cal difference  be- 


tween man  and 
other  animals,  but 
man's  mind  iso- 
lates him  among 
the  other  animals 
still  more. 

The  human 
species  is  divided 
into  five  varieties 
or  races:  1.  Cau- 
casian ( Fig.  1 ). 
Skin  fair,  hair  wavy,  eyes  oval.  (Europe  except  Finns 
and  Lapps,  Western  Asia,  America. )  2.  Mongolian.  Skin 
yellow,  hair  straight  and  black,  face  flat,  nose  blunt,  almond 
eyes.  (Central  Asia,  China,  Japan,  Lapps  and  Finns  of 
Europe,  Eskimos  of  North  America.)  3.  Americans.  Skin 
copper  red,  hair  straight,  nose  straight  or  arched.  (North 
and  South  America.)  4.  Malay.  Skin  brown,  face  flat, 
hair  black.     (Australia  and  Islands  of  Pacific.)     5.   EtJii- 


FiG.  1.— Facial  Angles  of  Caucasian  (nearly  900) 
and  Ethiopian  (about  700).  The  angle  between 
lines  crossing  at  front  of  upper  jaw  near  I  ase  of 
nose,  one  line  drawn  from  most  prominent  part  of 
forehead,  the  other  through  hole  of  ear. 


2  HUMAN  BIOLOGY 

opian  (Fig.  i).  Skin  dark,  hair  woolly,  nose  broad,  lips 
thick,  jaws  and  teeth  prominent,  forehead  retreating,  great 
toe  shorter  than  next  toe  and  separate.    (Africa,  America.) 

There  is  a  struggle  between  the  races  for  the  possession  of  different 
lands.  The  Caucasian  is  gaining  in  Australia.  Africa,  and  America. 
With  difficulty  the  Mongolians  are  kept  from  the  western  shores  of 
America.  The  Ethiopian  in  America  shows  a  lessened  rate  of  increase 
every  decade  ;  this  may  be  due  to  the  tendency  of  the  race  to  crowd  into 
cities  and  the  strain  of  suddenly  changing  from  jungle  life  in  less  than 
two  centuries.  Civilization  is  a  strain  upon  any  race.  It  is  destroying 
the  American  Indian.  The  Mongolian  and  Caucasian  survive  civiliza- 
tion best,  but  insanity  is  increasing  rapidly  among  the  latter. 


Fig.  2.  —  Indian  Weapons  :  Lance  and  Arrow  Heads. 
From  a  bank  of  mussel  shells  (remains  of  savage  feast)  at  Keyport,  N.J. 

Man's  Original  Environment.  —  Primitive  man  lived  without  the  use 
of  fire  or  weapons  other  than  sticks  or  stones.  His  first  home  was  in 
the  tropics,  where  his  needs  were  readily  supplied,  and  probably  in 
Asia.  Many  nations  have  a  tradition  of  a  home  in  a  garden  (Greek, 
paradisos).     His  food  was  chiefly  tree  fruits  and  nuts.     When  because 

of  crowding  he  left  nature's 
garden,  he  acquired  skill  in 
hunting  and  fishing  and  the 
use  of  fire  that  flesh  might  sup- 
plement the  meager  fruits  of 
colder  climates.  His  weapons 
were  of  rough  (chipped)  stone 
at  first  —  in  the  old  stone  age. 
In  this  age  the  mammoth  lived. 
He  learned  to  polish  implements  in  the  new  stone  age.  The  Indians 
were  in  that  stage  when  Columbus  came  to  America  (Figs.  2,  3).  The 
cultivation  of  grain  and  the  domestication  of  animals  probably  began 
in  this  age.     The  bronze  and  iron  ages  followed  the  stone  age. 


Fig.  3. 


Indian  Tomahawk. 
Stone.     Keyport,  N.J. 


Polished 


INTRODUCTION 


The  Reaction  between  Man  and  his  Environment.  —  The  estimates 
by  various  geologists  of  the  time  man  has  existed  as  a  species  vary 
from  20,000  to  200,000  years.  The  active  life  out  of  doors  which  man 
led  for  ages  (Fig.  4)  has  thoroughly  adapted  his  body  only  for  such  a 
life.  Now  steam  and  other  forces  work  for  him.  and  his  muscles 
dwindle ;  his  lungs  are  seldom  fully  expanded,  and  the  unused  portions 
become  unsound ;  he  lives  in  tight  houses,  and  the  impure  air  makes 
his  blood  impure  and  his  skin  delicate  ;  he  eats  soft  concentrated  food, 
and  his  teeth  decay  and  his  too  roomy  food  tube  becomes  sluggish. 
His  nerves  and  brain  are  fully  active  and  they  become  unsound  from 
overwork  and  impure  blood. 1 


Fig.  4.  —  Primitive  Man,  showing  clothing  and  weapons  of  chase  and  war. 


Degeneration  of  Unused  Parts.  —  Several  facts  just  stated  illustrate 
the  biological  law  that  disuse  causes  degeneration. 

Man's  Modification  of  his  Environment. — The  energy  of  the  world, 
whether  of  coal,  waterfall,  oil,  forest,  or  rich  soil,  has  the  sun  as  its 
source.  All  of  these  are  being  destroyed  by  man,  often  with  recklessness 
and  wantonness.  The  promised  land  which  "flowed  with  milk  and 
honey  "is  now  almost  a  desert.  Other  examples  are  Italy,  Carthage, 
Spain.  The  destruction  of  forests  causes  floods  which  wash  away  the 
soil.  //  is  estimated  that  there  are  only  one  fourth  as  many  song  birds 
in  the  United  States  as  there  were  fifteen  years  ago.  Insects  and  weeds 
or  deserts  replace  rich  soil,  noble  quadrupeds,  singing  birds,  and  stately 
trees.     Many  farmers,  however,  preserve  the  fertility  of  the  soil. 

To  the  erect  posture  is  due  man's  free  use  of  his  hands  and  the 
cooperation  of  hands  and  senses.     This  has  given  man  his  intellectual 

1  It  has  been  prophesied  that  the  future  man  will  be  a  brownie-like  crea- 
ture with  near-sighted  eyes,  shrunken  body,  slim  little  legs  and  arms,  large 
hairless  head,  toothless  gums,  a  stomach  using  only  predigested  food,  muscles 
suited  only  to  push  an  electric  button  or  pull  a  lever,  and  mind  very  active. 
But  this  disregards  the  indispensable  need  of  a  sound  mind  for  a  sound  body. 
There  cannot  even  be  a  play  of  emotion  without  a  change  in  the  circulation. 


4  HUMAN  BIOLOGY 

development.  The  erect  position  has  given  greater  freedom  to  the 
chest.  Man  uses  fewer  organs  of  locomotion  than  any  other  animal. 
The  opossum  lias  two  hands,  but  they  are  on  the  hind  limbs.  The 
ape  has  four  hands,  but  must  use  them  all  in  locomotion.  (What  is  a 
hand  ?)  The  erect  position,  however,  makes  spinal  deformity  easier  to 
acquire,  and  the  whole  weight  being  upon  one  hip  at  each  step  man  is 
liable  to  hip-joint  diseases.  In  the  horizontal  trunk  the  organs  lie  one 
behind  another;  in  man  they  lie  one  upon  another,  and  are  more  liable 
to  crowding  and  displacement.  The  prone  position  in  sickness  helps 
to  restore  them.  Large  blood  vessels  at  neck,  armpits,  and  groins, 
which  occupy  protected  positions  in  quadrupeds,  are  held  to  the  front 
and  exposed  to  danger.  The  open  end  of  the  vermiform  appendix  and 
of  the  windpipe  are  upward  in  the  erect  trunk  of  man.  Valves  are 
lacking  in  some  vertical  veins  and  present  where  little  needed  in  hori- 
zontal veins.  But  the  freedom  of  the  hands  more  than  makes  up  for 
all  the  disadvantages  of  erectness. 

The  Survival  of  the  Fittest.  —  Those  who  do  not  work  degenerate. 
Those  who  overwork,  or  work  with  only  a  few  organs,  as  the  brain  and 
nerves,  degenerate.  The  workers  survive  and  increase  in  numbers,  the 
idle  perish  and  leave  few  descendants. 

What  rate  of  adjustment  to  new  environment  is  possi- 
ble for  man?  This  has  not  been  ascertained;  it  is  prob- 
ably much  slower  than  has  been  generally  imagined.  The 
natives  of  Tasmania,  New  Zealand,  and  many  of  the 
Pacific  Islands  became  extinct  in  less  than  a  century  after 
adopting  clothing  and  copying  other  habits  from  Euro- 
peans. Life  in  the  country  in  civilized  lands  differs  less 
from  the  environment  of  primitive  man  than  does  life  in 
cities.  Cities  have  been  likened  to  the  lion's  cave  in  the 
fable,  to  which  many  tracks  led,  but  from  which  none  led. 
The  care  of  health  in  cities  is  now  making  rapid  strides 
along  the  biological  basis  of  purer  air,  more  open  space,  less 
noise,  simple  food,  and  pure  water.  Biology,  by  supplying 
as  a  standard  the  conditions  which  molded  man's  body 
for  ages,  furnishes  a  simple  and  sure  basis  for  hygiene. 
To  mention  one  instance  among  many,  man  blundered  for 
centuries  in  attempting  the  cure  of  consumption,  and  well- 


INTRODUCTION 


nigh  gave  up  in  despair.  Yet  it  has  recently  been  shown 
that  if  the  sufferer  returns  only  in  a  measure  to  the  open- 
air  habits  of  his  remote  ancestors,  tuberculosis  is  one  of 
the  most  curable  of  diseases.  The  biological  guide  to 
health  is  surer  and  simpler  than  tinkering  with  drugs,  fuss- 
ing with  dietetics,  and  avoiding  exposure.  Man  is  of  all 
animals  least  thoroughly  adjusted  to  his  environment,  be- 
cause of  his  continual  and  rapid  progress.  Disease  may 
be  defined  as  the  process  by  which  the  body  adapts,  or  at- 
tempts to  adapt,  itself  to  so  sudden  a  change  of  environ- 
ment that  some  organ  has  failed  to  work  in  harmony  with 
the  others.  By  disease  the  body  comes  into  adjustment 
with  the  new  condition,  or  attempts  to  do  so. 

Protoplasm.  —  The  life  and  growth  of  man's  body,  as 
the  life  and  growth  of  all  animals  and  plants,  depend  upon 
the  activity  of  the  living 
substance  called  proto- 
plasm, as  manifested  in 
minute  bodies  called  cells. 
In  fact,  protoplasm  can- 
not exist  outside  of  cells. 
The  cells  of  the  human 
body  and  their  relation  to 
the  body  as  a  whole  will 
next  be  considered. 


FIG.  5.  —  An  Ameba,  highly  magnified. 
iiu,  nucleus;  psd,  false  foot. 


The  Ameba.  —  Of  all  the 
animal  kingdom,  the  minute 
creatures  that  can  be  seen  only  with  a  microscope  are  most  different  from 
man.  One  of  the  most  interesting  of  these  is  the  a-me'ba  (Fig.  5  ; 
spelled  also  amaba,  see  Animal  Biology,  Chap.  II).  A  thousand  of 
them  placed  in  a  row  would  hardly  reach  an  inch.  Some  may  doubt 
whether  the  ameba  is  a  complete  animal.  Study  the  figures  of  it,  and 
no  head,  or  arms,  or  legs,  or  mouth  can  be  found.  It  appears,  when 
still,  to  be  merely  a  lump  of  jelly.  But  the  ameba  can  push  out  any 
part  of  its  body  as  a  foot,  and  move  slowly  by  rolling  its  body  into  the 


Ill' MAN  BIOLOGY 


Fig.  6. — A  White  Blood  Cell,  magnified;  forms 
noticed  at  intervals  of  one  minute. 


foot.  //  can  put  out  any  part  of  its  body  as  an  arm,  and  take  in  a 
speck  of  food  :  or,  if  the  food  happens  to  be  near,  the  ameba  can  make 
a  mouth  in  any  part  of  its  body,  and  swallow  the  food  by  closing  around 
it  (Animal  Biology,  Fig.  12).  The  ameba  has  no  lungs,  but  breathes 
with  all  the  surface  of  its  body.  Any  part  of  its  body  can  do  anything 
that  another  part  can  do.  When  the  ameba  grows  to  a  certain  size,  Lt 
multiplies  by  squeezing  together  near  the  middle  (Animal  Biology,  Fig. 
13)  and  dividing  into  two  parts.  Amebas  have  not  been  observed  to 
die  of  old  age;  starvation  and  accident  aside,  they  are  immortal. 

The  Ameba  and  Man  Compared.  —  The  microscope  shows  us  that  the 
skin,  the  muscles,  the  blood,  —  in  fact,  all  parts  of  the  body,  —  contain 

numberless  small 
parts  called  cells. 
These  cells  are 
continually  chang- 
ing with  the  activi- 
ties of  the  body. 
One  of  the  most 
interesting  kinds 
of  cells  we  shall  find  to  be  the  white  blood  cells,  or  corpuscles.  One  is 
shown  in  Fig.  6,  with  the  changes  that  it  had  undergone  at  intervals 
of  one  minute.  The  thought  readily  occurs  that  these  cells,  although 
part  of  marts  body,  resemble  the  ameba  that  lives  an  independent  life. 
A  man  or  a  horse  or  a  fish  —  in  fact  any  animal  not  a  protozoan  —  has 
something  of  the  nature  of  a  colony,  or  collection,  of  one-celled  ani- 
mals. We  are  now  prepared  to  understand  a  little  as  to  how  the  body 
grows,  and  how  a  cut  in  the  skin  is  re- 
paired. The  cells  take  the  nourishment 
brought  by  the  blood,  use  it,  and  grow 
and  multiply  like  the  ameba.  Thus  new 
tissue  is  formed.  All  animals  and  vege- 
tables—  that  is  to  say,  all  living  things 
—  are  made  of  cells. 

A  living  cell  akvays  contains  a 

still  smaller  body  called  a  nucleus 

Fig.  7.  —  Diagram  of  a 
(Fig.  7).     There  is  sometimes  a  Cell 

Small     dot     in    the    nUCleUS,    Called       /,  protoplasm;    «,  nucleus;    «',  nu- 

the  nucleolus.      The  main  body  of 

the  cell  consists  of  the  living  substance  called  protoplasm,  con- 
taining nitrogen.     Usually,  but  not  always,  there  is  a  wall 


INTR  OD  UCTION  7 

surrounding  the  cell,  called  the  cell  wall.  Workers  with 
the  microscope  found  long  ago  that  animals  and  plants  are 
constructed  of  little  chambers  which  they  called  cells.  It 
was  found  later  that  the  soft  contents  in  the  little  chambers 
is  of  more  importance  than  the  walls  which  the  protoplasm 
builds  around  itself.  A  living  cell  is  not  like  a  cell  in  a 
honeycomb  or  a  prison.  In  biology  we  define  a  cell  as  a 
bit  of  protoplasm  containing  a  nucleus.  No  smaller  part  of 
living  matter  can  live  alone.  The  protoplasm  of  the  nu- 
cleus is  called  nucleoplasm ;  the  rest  of  the  protoplasm  is 
called  cytoplasm. 

A  fiber  is  threadlike,  and  is  either  a  slender  cell  (Fig.  8), 
a  slender  row  of  cells  (Fig.  10),  or  a  branch  of  a  cell.     A 


Fig.  8.  — A  CELL  (from  involuntary  muscle),  so  slender  that  it  is  called  a  fiber. 

tissue  is  defined  as  a  network  of  fibers  or  a  mass  of  similar 

cells  serving  the  same  purpose,  or  doing  the  same  work.     A 

membrane  is  a  thin  sheetlike  tissue. 

The  Nature  of  the  Human  Body.  —  The  human  body  is  a 

community  of  cells,  and  may  be  compared  to  a  community 

of  people.     It  is  a  crowded  community,  for  all  the  citizens 

live  side  by  side  as  they  work.      They  are  so  small  that  it 

takes  several  hundred  of  them  to  make  a  line  an  inch  long. 

We  should  never  have  suspected  the  existence  of  cells  had 

it  not  been  for  the  microscope ;  but  now  we  know  that 

they  eat  and  breathe  and  work  and  divide  into  young  cells 

which  take  the  place  of  the  old  ones. 

A  child  that  is  born  in  a  community  of  people  may  become  a  railroad 
man  and  carry  food  and  other  freight  from  place  to  place ;  so,  in  the 
great  community  of  cells  (see  Fig.  9)  making  up  the  human  body,  the 
red  blood  cells,  like  the  railroad  man,  are  employed  in  carrying  material 
from  place  to   place.     But   the   community   is   old-fashioned,  for  the 


8 


HUMAN  BIOLOGY 


i/erveceiti 


Cells  from 


m 
Sie/MUtli 


Ce/tsfromtfie  windpipe 
^Muscle  cei/s 


citizens  build  canals  instead  of  railroads  for  their  commerce  (see  Fig. 
84).  Just  as  a  child  may  grow  up  to  be  a  farmer  and  aid  in  the  con- 
version of  crude  soil  into  things  suitable  for  the  use  of  man,  so  the 
digestive  cells  take  the  food  we  eat  and  change  it  into  material  with 
which  the  cells  can  build  tissue.  Some  of  the  citizens  of  a  community 
must,  at  times,  take  the  part  of  soldiers  and  policemen,  and  protect  the 

community  against 
the  attacks  of  ene- 
mies. The  white  blood 
cells,  already  referred 
to,  may  be  called  the 
soldiers  ;  for  they  go 
to  any  part  attacked 
by  injurious  germs,  a 
particle  of  poison,  or 
other  enemy,  and  try 
to  destroy  the  ene- 
mies by  devouring  or 
digesting  them.  At 
other  times  they  help 
to  repair  a  break  in 
the  skin.  If  a  splin- 
ter gets  into  the  skin,  the  white  blood  cells  form  a  white  pus  around 
the  splinter  and  remove  it.  In  fact,  the  white  blood  cell  has  been  re- 
ferred to  as  a  kind  of  fack-at-all-irades.  In  the  human  community 
there  are  certain  persons  who  reach  the  positions  of  teachers,  law- 
makers, and  governors ;  they  instruct  and  direct  the  other  members  of 
the  community.  Just  so,  in  the  community  of  cells,  there  are  certain 
cells  called  nerve  cells  (see  Fig.  11)  that  have  the  duty  of  governing 
and  directing  the  other  cells.  The  nerve  cells  are  most  abundant  in 
the  brain.  Large  cities  must  have  scavengers.  Likewise  in  the  human 
body,  a  community  composed  of  millions  of  cells,  there  are  certain  cells 
in  the  skin  and  the  kidneys  which  have  this  duty.  They  are  continually 
removing  impurities  from  the  body.1 

Division  of  Labor.  —  There  is  a  great  advantage  in  each 
cell  of  the  human  body  having  its  special  work,  instead  of 
having  to  do  everything  for  itself,  as  each  ameba  cell  must 
do.  Under  this  system  each  cell  can  do  its  own  work  better 
than  a  cell  of  any  other  kind  can  do  it.     Among  wild  tribes 

1  From  Coleman's  "  Hygienic  Physiology,"  The  Macmillan  Co.,  N.Y. 


Fig.  9.  —  Various  Cells  of  the  body.     (Jegi.) 
Tiny  citizens  of  the  bodily  community. 


INTRODUCTION  9 

f 
there  is  very  little  division  of  labor.     Each  man  makes  his 

own  weapons,  each  knows  how  to  weave  coarse  cloth,  how 
to  cook,  how  to  farm,  etc.  Savages  do  not  have  as  good 
weapons  as  do  people  who  leave  the  making  of  weapons  to 
certain  men  whose  special  business  it  is.  What  kind  of 
pocketknives  or  pencils  do  you  think  the  boys  of  this 
country  would  have  if  each  boy  had  to  make  his  own 
pocketknife  or  pencil  ?  What  kind  of  scissors  and  thread 
would  the  girls  have  if  each  girl  had  to  make  them  her- 
self ?  Our  muscle  cells  can  contract  better  than  the 
ameba ;  the  cells  in  the  lungs  can  absorb  oxygen  better 
than  the  ameba.  We  have  just  as  great  an  advantage  in 
digestion,  feeling,  and  other  processes  ;  for  the  ameba  eats 
without  a  mouth,  digests  without  a  stomach,  feels  without 
nerves,  breathes  without  lungs,  and  moves  without  muscles. 
Division  of  labor  between  the  sexes  also  occurs  among 
the  higher  animals.  Those  who  desire  that  man  and 
woman  should  have  the  same  education  and  work  would 
violate  the  biological  law  of  "progress  by  specialization," 
which  could  only  cause  race  degeneration. 

A  part  of  the  body  which  is  somewhat  distinct  from 
surrounding  parts,  and  has  special  work  to  do,  is  called  an 
organ ;  the  special  work  which  the  organ  does  is  called  its 
function.  The  eye  is  the  organ  of  sight.  The  skin  is  an 
organ  ;  its  function  is  to  protect  the  body.  This  book  will 
treat  of  (1)  the  structure,  appearance,  and  position  of  each 
organ,  or  anatomy;  (2)  the  function  of  each  organ,  or 
physiology;  (3)  the  conditions  of  health  for  each  organ, 
or  hygiene ;  (4)  the  conditions  under  which  each  organ 
worked  in  the  primitive  life  of  the  race ;  (5)  the  effects  of 
change  of  environment ;  (6)  the  anatomy  of  man  compared 
with  the  lower  animals.  (5)  belongs  to  the  science  of 
Ecology.    These  sciences  are  parts  of  the  science  of  Biology. 


IO 


HUMAN  BIOLOGY 


Fig.  io.  —  Three 
Muscle  Fibers 
from  the  heart 
(showing  the  nu- 
clei of  six  cells). 


The  Tissues.  —  As  the  organs  have  dif- 
ferent functions,  they  must  have  different 
structures  that  they  may  be  adapted  to  their 
work.  Just  as  a  house  must  have  brick 
for  the  chimney,  shingles  for  the  roof, 
and  nails  to  hold  the  timbers  and  other 
parts  together,  so  the  body  has  various 
tissues  to  serve  different  purposes.  The 
bones  must  not  be  constructed  like  the 
muscles,  and  the  muscles  cannot  be  like 
the  skin.  The  chief  work  of  the  cells  is 
to  construct  the  tissues  and  repair  them. 
During  life  changes  are  constantly  going 
on.  Careful  little  workmen  are  keeping 
watch  over  every  part  of 
the  body;  thrifty  little 
builders  are  busy  in  repairing  and  restor- 
ing. No  sooner  is  one  particle  removed 
than  another  takes  its  place.  In  one  di- 
rection the  cells,  acting  as  undertakers,  are 
hurrying  away  matter  which  is  dead  ;  in 
the  other  direction  the  unseen  builders 
are  filling  the  vacant  places  with  matter 
that  is  living. 

The  Seven  Tissues.  —  There  are  seven 
kinds  of  tissues.  Two  of  them,  the  mus- 
cular and  nervous  tissues,  are  called  the 
master  tissues,  since  they  control  and  ex- 
pend the  energies  of  the  body.  The  other 
five  tissues  are  called  the  supporting  tis- 
sues, since  they  supply  the  energy  to  the 
master  tissues,  support  them  in  place, 
nourish  and  protect  them. 


Fig.  ii.—  Nerve 
Cells,  showing 
their  branches 
interlacing. 


INTRODUCTION 


II 


Fig.  12. —  Connective  Tissue  Cells, 
removed  from  among  the  fibers  of 
Fig.  13- 

>/,  c,  nucleus;  /.  branches. 


The  Master  Tissues.  —  The  muscular  tissue  consists 
chiefly  of  rows  of  cells  placed  end  to  end  (Fig.  10).  These 
cells  have  the  remarkable  property  of  becoming  broader 
and  shorter  when  stimulated  by  impulses  from  nerve  cells 

The  nerve  tissue  consists 
of  cells  with  long,  spiderlike 
branches  (Fig.  u).  Some 
nerve  cells  have  branches 
several  feet  long,  so  long  that 
they  go  from  the  backbone 
to  the  foot.  The  branches 
are  called  nerve  fibers  (Fig. 
142).  Nerve  fibers  which 
carry  impulses  to  the  nerve 
cells  are  called  sensory  fibers. 
The  nerve  fibers  which  carry 
impulses  from  the  nerve  cells 
are  called  motor  fibers.  The 
organs  are  set  to  work  by 
impulses  through  the  motor 
fibers.  Besides  these  two 
master  tissues  there  are  five 
supporting  tissues. 

Connective  tissue,  like  all 
other  tissues,  contains  cells 
(see  Fig.  12),  but  it  consists 
chiefly  of  fine  fibers.  These 
fibers  are  of  two  kinds,  — 
very  fine  tvliite  fibers  which 
are  inelastic,  and  larger  yellow  fibers  which  are  very  elastic 
(see  Fig.  13).  Connective  tissue  is  found  in  every  organ, 
binding  together  the  other  tissues  and  cells.  It  is  inter- 
woven among  the  muscle   cells,  and   the   tendons   at   the 


Fig.  13. 


-Connective  Tissue 
Fibers. 


a,  b,  bundles  of  white  fibers;  c,  a  yellow 
fiber. 


12 


H I' MAN  BIOLOGY 


ends  of  the  muscles  are  composed  almost  wholly  of  it.  If 
every  other  tissue  were  removed,  the  connective  tissue 
would  still  give  a  perfect  model  of  all  the  organs.  How 
abundant  this  tissue  is  in  the  skin  may  be  known  from  the 
fact  that  leather  consists  entirely  of  it. 

Fatty  (Adipose)  Tissue.  —  Fatty  tissue  is  formed  by  the 
deposit  of  oil  in  connective  tissue  cells  (see  Fig.  14).     Fat  is 

held  in  meshes  of 
connective  tissue 
fibers.  That  fatty 
tissue  consists  not 
alone  of  fat,  but  of 
fibers  also,  is  shown 
when  hog  fat  is 
rendered  into  lard, 
certain  tough  parts 
called  "crack- 
lings" being  left. 
What  is  the  differ- 
ence between  beef 
fat  and  tallow  ? 

Epithelial  tissue 
consists  of  one  or 
more  layers  of  dis- 
tinct cells  packed 
close  together  (see 
Fig.  15).  It  con- 
tains no  connective  tissue  or  other  fibers,  and  is  the  simplest 
of  the  tissues.  Epithelial  tissue  forms  the  outer  layer  of 
the  skin,  called  the  epidermis,  and  the  mucous  membrane 
lining  the  interior  of  the  body.  It  contains  no  blood  ves- 
sels, the  epithelial  cells  obtaining  their  nourishment  from 
the  watery  portion  of  the  blood  which  soaks  through  the 


Fig.  14.  —  Fatty  Tissue.     Five  fat  cells,  held  in 
bundles  of  connective  tissue  fibers. 

a  is  a  large  oil  drop;   m,  cell  wall;  nucleus  (n)  and  proto- 
plasm (/)  have  been  pushed  aside  by  oil  drop  (a). 


INTRODUCTION 


13 


underlying  tissues.  Epithelial  cells  are 
usually  transparent ;  for  instance,  the 
blood  is  visible  beneath  the  mucous 
membrane  of  the  lips.  The  finger  nails 
are  made  of  epithelial  cells,  and  they 
are  nearly  transparent. 

There  are  two  classes  of  epithelial 
cells ;  one  class  forms  protective  cover- 
ings(Fig.  15)  ;  the  other  class  forms  the 
lining  of  glands  (Fig.  16).  Glands  are 
cavities  whose  lining  of  epithelial  cells 
(Fig.  17)  form  either  useful  fluids  called 
secretions  to  aid  the  body  in  its  work,  or 
harmful  fluids  called  excretions  to  be  cast 
out,  or  excreted.  Most  glands  empty 
their  fluids  through  tubes  called  ducts. 

Cartilag'inous  tissue  is  tough,  yet 
elastic.  Cartilage  or  gristle  may  be 
readily  felt  in  the  ears,  the  windpipe, 
and  the  lower  half  of  the  nose.  This 
tissue  consists  of  cartilage  cells  embedded 
in  an  intercellular  substance  through 
which  run  connective  tissue  fibers  (see 
Fig.  18).  If  yellow  fibers  predominate, 
the  cartilage  is  yellow  and  very  elastic, 
as  in  the  ear  ;  if  white  fibers  predomi- 
nate, it  is  white  and  less  elastic,  as  in 
the  pads  of  gristle  between  the  bones 
of  the  spinal  column.  Cartilage  is  to 
prevent  jars,  and,  in  movable  joints,  to 
lessen  friction. 

Bony  (Osseous)  Tissue.  —  Solid  bone 
is  seen  under  the  microscope  to  contain 


Fig.  15.  — Epithelial 
Tissue  (epidermis  of 
skin,  magnified). 


•*Sw«Sf 


Fig.  16.  — Epithelial 
Tissue;  cells  form- 
ing two  glands  in 
wall  of  stomach. 


Fig.  17.  — Six  Gland 
Cells  :  at  left, 
shrunken  after  activ- 
ity ;  at  right,  rested, 
full  of  granules. 


H 


HUMAN  BIOLOGY 


m» 


many  minute  cavities  (Fig.  19).     ///  these  cavities  the  bone 
cells  lie  self-imprisoned  in  walls  of  stone  ;  for  these  cells 

have  formed  the  bone  by  deposit- 
ing limestone  and  phosphate  of 
lime  around  themselves.  There 
are  minute  canals  (3,  Fig.  19), 
however,  through  which  nourish- 
ment comes  to  the  cells.  The 
watery  portion  of  the  blood  passes 
through  these  small  canals  from 
the  blood  vessels  that  flow  through 
the  larger  canals  (1,  Fig.  19). 
Bone  cells  may  live  for  years,  al- 
though some  of  the  other  cells  of 
the  body  live  only  a  few  hours. 

New  cells  to  repair  the  tissues  are 
formed  by  subdivision  of  the  cells,  as 
with  the  ameba.  Unlike  protozoans, 
many-celled  animals  are  mortal  because 
the  outer  cells  prevent  the  deeper  cells 
from  purifying  themselves  perfectly  and 
obtaining  pure  food  and  oxygen.  Even 
the  arteries  of  an  old  man  become  hard- 
ened by  the  deposit  of  mineral  matter 
which  the  body  has  been  unable  to  ex- 
crete. 


igp 


Fig.  18.  -Cartilaginous 
Tissue.  A  thin  slice  highly 
magnified. 

a,  b,  c,  groups  of  cells;   m,  inter- 
cellular substance. 


^f&ms^k 


The  body  is  kept  alive  and 
warm  by  burning,  or  oxidation. 
One  fifth  of  the  air  is  oxygen  gas. 
We  breathe  it  during  every  min- 
ute of  our  existence.  It  is  car- 
ried by  the  blood  to  all  the  tis- 
sues. Not  one  of  the  cells  could 
work  without  oxygen.  Without  it  the  body  would  soon  be 
cold  and  dead,  for  oxygen  keeps  the  body  alive  and  warm 


Fig.  19.  —  Bony  Tissue.  Thin 
slice  across  bone,  as  viewed 
through  microscope. 

Larger  blood  tubes  pass  through 
the  large  holes  (i);  the  cavities 
containing  bone  cells  lie  in  cir- 
cles, and  are  connected  by  fine 
tubes  (3)  with  the  larger  tubes. 


INTRODUCTION 


15 


by  uniting  in  the  cells  with  sugar,  fat,  and  all  other  sub- 
stances in  the  body  except  water  and  salt.  Oxygen  burns 
or  consumes  the  substances  with  which  it  unites,  and  the 
process  is  called  oxidation.  Hence  the  cells  have  to  be 
continually  growing  and  multiplying  to  repair  the  tissue 
and  replace  the  material  used  up  by  oxidation.  Sugar  and 
flour  and  fat  oxidize,  or  burn,  outside  of  the  body,  as  well 
as  in  it,  as  can  be  proved  by  throwing  them  into  a  fire. 
Water  and  salt  are  two  foods  that  do  not  burn.  Hence 
they  can  furnish  no  heat  or  energy  to  the  body.  Water 
puts  out  a  fire  instead  of  helping  it,  and  so  does  salt. 
Throw  salt  into  a  fire  or  on  a  stove;  it  will  pop  like  sand, 
but  will  not  burn. 

The  cells  need  the  oxygen  of  fresh  air ;  they  need  food 
for  the  oxygen  to  unite  with,  but  they  are  injured  by  many 
substances  called  poisons.  Arsenic  destroys  the  red  blood 
cells.  Strychnine  attacks  the  nerve  cells  in  the  spinal 
cord.  Alcohol  attacks  the  epithelial  cells  lining  the 
stomach  and,  when  it  is  absorbed,  attacks  the  nerve  cells 
and  other  cells.     Morphine  attacks  the  nerve  cells. 

Written  Exercises.  —  Draw  a  series  of  seven  pictures  to  show  the 
seven  tissues  (Figs.  10,  14,  15,  18,  19).  Write  the  "Autobiography" 
of  a  White  Blood  Cell  (see  also  pages  59  and  68).  The  Rewards  of 
Caring  for  the  Health.  Health  and  the  Disposition.  Which  is  more 
important,  a  Thorough  Knowledge  of  Geography  or  of  Physiology? 
Five  Things  which  people  Value  above  Health  (and  lose  health  to  ob- 
tain). The  Blessings  that  follow  Good  Health.  The  Tissues  Com-, 
pared  (function,  proportion  of  cells,  intercellular  material  and  fibers, 
activity,  rate  of  change). 

See  also  pages  50,  1 16.     Pupils  should  choose  their  own  subjects. 


CHAPTER    II 

THE   SKIN 

Note  to  Teacher.  —  The  experiments  should  be  assigned  in  turn 
to  the  pupils  as  each  chapter  is  reached  :  e.g.  this  set  of  13  will  leave  3 
pupils  in  a  class  of  39  to  stand  responsible  for  each  experiment.  Each 
pupil  should  do  the  work  separately  and  credit  may  be  given  for  the 
best  results.  Encourage  (or  require)  each  pupil  to  try  every  experi- 
ment and  record  them  in  a  note  book. 

Experiment  1.  (At  home  or  in  class.)  Albinism.  —  Study  a  white 
rabbit  as  an  example  of  albinism.  Does  albinism  affect  only  the  skin? 
What  evidence  that  its  blood  is  of  normal  color? 

Experiment  2.  Use  of  Hairs  on  the  Skin.  —  Let  one  pupil  rest  his 
hand  upon  the  desk  behind  him  while  another  touches  a  hair  on  his 
hand  with  a  pencil.  He  should  speak  at  the  moment,  if  it  is  felt.  Do 
the  hairs  increase  the  sensitiveness  of  the  skin?  What  was  their  use 
with  primitive  man?  Are  the  hands  of  all  your  acquaintances  equally 
hairy?  Are  the  hairs  to  be  classed  as  rudimentary?  Will  they  disap- 
pear?    Will  the  race  become  baldheaded? 

Experiment  3.  (Home  or  school.)  Invisible  Perspiration.  —  Hold 
a  piece  of  cold  glass  near  the  hand  or  place  the  cheek  near  a  cold  win- 
dow pane  and  notice  for  evidence  of  moisture.     Its  source? 

Experiment  4.  —  Effect  of  Evaporation  on  Temperature.  —  Read  a 
thermometer  and  cover  its  bulb  with  a  moist  cloth.  Read  again  after 
twenty  minutes.    Repeat  experiment  in  breeze. 

Experiment  5.  Moisten  one  hand  and  allow  it  to  dry.  Touch  the 
other  hand  with  it.     Explain  result. 

Experiment  6.  Absorbing  Power  of  Fabrics. — Wet  the  hands  and 
dry  them  upon  a  piece  of  cotton  cloth.  Repeat  with  woolen,  linen,  and 
silk.     Arrange  in  list  according  to  readiness  in  absorbing  water. 

Experiment  7.  Rates  of  Drying.  —  Immerse  the  cloths  in  water  and 
hang  them  up  to  dry.  Test  their  rates  of  drying  with  dry  powder  or  by 
touch. 

Experiment  8.  Test  Looseness  of  Weave  of  above  cloths  by  measur- 
ing the  distance  pieces  of  equal  length  will  stretch. 

Experiment  9.  Does  Cotton  or  Wool  protect  better  from  Radiant 
Heat?  —  Lay  a  thermometer  in  the  sun  for  ten  minutes,  first  covering 

16 


OF  THE 

UNIVERSITY 

OF 


Colored  FIGURE  i. — Section  of  Skin  (diagram,  enlarged  25  times).      On  the  left 
the  connective  tissue  fibers  of  the  true  skin  are  shown. 

In  cutis  (c»,  or  dermis,  find  capillaries,  nerve  fibers,  fat  cells,  two  sweat  glands  and  ducts,  four 
oil  glands  (two  in  section),  two  hsirs,  three  nerve  papillae,  five  papillae  containing  capillaries, 
tivo  muscles  for  erecting  hairs.      In  epidermis  find  flat  cells,  round  cells,  and  pigment  cells. 


Fig.  2.  —  Where 
the  Food  is 

ABSORBED    (villus   of 

intestine). 

Fir,.  3.  — Where 

the  Food  is 

USED   (cells  with 

lymph  spaces). 


/fusc/e  eel's 


B/ooa  ca/n//ory 


''i-Lymp/i 


/, /,  jaws:   ol,  nerve  of  smell : 
ofi,     nerve    of    sight  :     b, 
brain;  /,  tongue;   e/>,  epi    ch, 
glottis;     oe,    gullet 
t!i,  thymus  gland; 
Ig,  lung;  //,  heart; 
/,  liver;  g,  stom- 
ach; s.  spleen;       t 
/,  pancreas ; 
k,  kidney;  d 
diaphragm ; 
m,  muscle; 
u,  bladder; 
ch,  spinal 
cord;   v,  ve 
tebrae. 


Fig.  4. — 
Idea  i-  Sec- 
~.         tion  of 
^       Mammal. 


Compare  with  oigans  of 
man  (colored  Fig.  6). 


THE   SKIN  17 

it  with  a  woolen  cloth.  Note  change  in  reading.  After  it  regains  first 
reading,  repeat,  covering  it  with  a  cotton  cloth  of  same  weight  and  tex- 
ture ?  Conclusion  ?  Expose  wrists  or  arms  to  sun  for  five  minutes,  one 
protected  by  the  cotton,  the  other  by  the  wool.     Result  ?     Conclusion? 

Experiment  10.  Rates  of  Heat  Absorption  and  Radiation  by  Different 
Colors.  —  Expose  thermometer  to  sunlight,  covered  successively  by  pieces 
of  cloth  of  same  thickness,  material,  and  texture.  Use  black,  blue,  red, 
yellow,  and  white  cloth.  Note  rise  of  temperature  for  equal  times  in  each 
case;  also  the  fall  of  temperature  for  equal  times  after  removal  to  shade. 

Experiment  11.  Effects  of  Dry  Powders.  —  Prepare  two  squares  from 
the  same  piece  of  leather  {e.g.  an  old  shoe).  Moisten  them  both,  and 
apply  face  powder  to  one.  Which  dries  more  quickly?  Repeat  after 
oiling  them.  Powder  a  portion  of  the  face  or  arm  daily  for  a  week  and 
compare  with  the  clean  portion. 

Experiment  12.  Dissect  the  kidney  of  an  ox  or  sheep,  making  out 
the  parts  mentioned  in  the  text,  p.  26. 

Experiment  13.  (In  class.)  Emergency  Drill.  —  Have  one  pupil  wet 
an  imaginary  burn  on  the  arm  of  another,  treat  it  with  flour  or  soda,  and 
bandage.     (See  text.) 

The  Skin  has  Two  Layers.  —  The  outer  layer  is  called  the 
epidermis ;  it  is  thinner,  more  transparent,  and  less  elastic 
than  the  inner  layer,  or  dermis.  The  epidermis  is  com- 
posed of  epithelial  cells  packed  close  together  (see  colored 
Fig.  1). 

The  dermis,  or  inner  layer,  is  a  closely  woven  sheet  of 
connective  tissue  (colored  Fig.  1)  containing  a  great  num- 
ber of  siveat  and  oil  glands,  roots  of  hairs,  blood  vessels, 
absorbent  vessels  (lymphatics),  and  nerves  (colored  Fig.  1). 
The  dermis  is  sometimes  called  the  true  skin  because  it  is 
of  greater  importance  than  the  epidermis.  It  is  united 
loosely  to  the  underlying  organs  by  a  layer  of  connective 
tissue.  It  is  in  this  layer  that  fat  is  stored.  The  upper 
surface  of  the  dermis  rises  into  a  multitude  of  projections 
(see  colored  Fig.  1)  called  papiV l<z  (singular,  papilla).  The 
epidermis  fits  closely  over  them  and  completely  levels  up 
the  spaces  between  them  except  on  the  palms  and  the 
soles.  Here  the  papillae  are  in  rows,  and  there  is  a  fine 
c 


HUMAN  BIOLOGY 


ridge  in  the  skin  above  each  row  of  papillae  (Fig.  24).  In 
the  papillae  are  small  loops  of  blood  vessels  and  sometimes 
a  nerve  fiber  (colored  Fig.  1). 

The  epidermis  is  composed  of  a  mass  of  cells  held  to- 
gether by  a  cement  resembling  the  white  of  an  egg.  The 
cells  near  the  surface  are  hard  and  flattened  ;  those  deeper 
down  near  the  dermis  are  round  and  soft  (see  Fig.  21). 

These  cells  are  liv- 
ing cells.  They  are 
kept  alive  by  the 
nourishment  in  the 
watery  portion  of 
the  blood  which 
soaks  through  from 
the  blood  tubes  in 
the  neighboring  pa- 
pillae. Hence  these 
cells  are  growing 
cells;  they  subdivide 
when  they  reach  a 
certain  size,  and  re- 
place those  wearing 
away  at  the  surface,  thus  constantly  repairing  the  epider- 
mis. The  dry  outer  cells  wear  away  rapidly.  They  have 
no  nuclei  and  are  dead  cells.  The  new  cells  forming  be- 
neath push  them  so  far  away  from  the  dermis  that  nour- 
ishment no  longer  reaches  them,  and  they  die. 

Pigment.  —  The  cells  in  the  lower  layers  of  the  epidermis 
contain  grains  of  coloring  matter,  or  pigment.  All  other 
cells  of  the  epidermis  are  transparent ;  the  pigment  has  the 
function  of  absorbing  and  arresting  light.  Albinos  or 
animals  entirely  without  pigment  have  pallid  skins  and 
pink  eyes  (Exp.  1). 


Fig.  20.  —  Epidermis 
of  Ethiopian. 


Fig.  21. —Epidermis 
of  Caucasian. 


THE   SKIN  19 

Immigrants  from  a  Cloudy  to  a  Sunny  Climate.  Adaptation.  —  The 
cells  of  the  deeper  tissues  can  readily  be  exhausted  by  the  stimulation 
of  too  much  light.  The  sunnier  the  climate,  the  greater  the  need  of 
pigment ;  hence  the  dark  skin  of  the  negro  and  the  blonde  skin  and 
hair  of  the  Norwegian.  European  immigrants  to  sunny  America  will 
o-row  darker.  The  Indian's  skin  is  better  suited  to  our  climate  than  is 
a  fair  skin.  Brunettes  have  a  better  chance  for  adaptation  than  blondes. 
The  American  type  when  developed  will  doubtless  be  brunette. 

The  hair  grows  from  a  pit  or  follicle  (Fig.  22).  Blood 
vessels  and  a  nerve  fiber  go  to  the  root  or  bulb  from  which 
a  hair  grows.  The  hair  will  grow  un- 
til this  papilla,  or  bulb,  is  destroyed 
(Exp.  2). 

Adaptation  of  the  scalp  to  a  tight  warm  cov- 
ering is  accomplished  through  the  shedding  of 
the  hair  rendered  useless  by  the  covering.  It  is 
impossible  to  stop  the  growth  of  superfluous  hair 
unless  the  hair  papillae  are  destroyed  with  an 
electric  needle,  such  is  the  vitality  of  hair ;  yet 

manv  men,  by  overheating  the  head  and  cutting 

~    ,        ...  .  ,     .  ,  ,  ,    ,      ,  1       Fig.    22.  —  Develop- 

off  the  circulation  with  tight  hats,  destroy  much 

,  ^^ .  MhNl     Ur     A     n  A  l  K 

of  the  hair  before  reaching  middle  age.       1  he  AND      Two      QlL 

health  of  the  hair  can  be  restored  and  its  loss  Glands. 

be  stopped  by  going  bareheaded  except  in  the 

hot  sun  or  in  extremely  cold  weather.  This  frees  the  circulation;  cold 
air  and  light  stimulate  the  cells  of  the  scalp.  Some  men  wear  hats, 
even  at  night  in  summer.  The  brain  needs  the  protection  of  the  hair. 
Beard  protects  the  larynx  or  voice  box,  which  is  large  and  exposed  in  man. 
It  was  also  a  protection  in  hunting  wild  beasts  and  in  war.  Compare 
mane  of  lion,  not  possessed  by  lioness.  "  Goose-flesh  "  after  a  cold  bath 
is  caused  by  the  contraction  of  small  muscles  (colored  Fig.  1),  raising 
the  now  tiny  hairs  in  an  absurdly  useless  effort  to  keep  the  body  warm. 

The  nails  are  dense,  thick  plates  of  epidermis  growing 
from  a  number  of  papilla?  situated  in  a  groove,  or  fold,  of 
the  skin  ;  there  are  many  fine  papillae  along  the  bed  from 
which  the  nail  grows.  Since  it  grows  from  its  under  side 
as  well  as  from  the  little  fold  of  skin  at  its  root,  the  nail  is 
thicker  at  the  end  than  near  the  root. 


20 


HUMAN  BIOLOGY 


Fig.  23.  — .4,  Development  of 
Sweat  Gland;  B,  Sweat 
Tube  Developed. 


The  oil  glands  empty  into  the  hair  follicles  (colored  Fig.  1 ). 
They  form  an  oil  from  the  blood  that  keeps  the  hair  glossy 

and  the  surface  of  the  skin  soft 
and  flexible  by  preventing  ex- 
cessive drying.  Hair  oil  should 
never  be  used  upon  the  hair,  as 
the  oil  soon  becomes  rancid,  and 
besides  causes  dust  and  dirt  to 
stick  to  the  hair. 

The  sweat  glands  (Fig.  23), 
like  the  hair  bulbs,  are  deep  in 
the  lowest  part  of  the  dermis. 
A  sweat  gland  has  the  form  of  a 
tube  coiled  into  a  ^//(colored  Fig.  1).  This  tube  continues 
as  a  duct  through  the  two  layers  of  skin,  and  its  opening 
at  the  surface  is  called  a  pore  (Fig.  24).  The  perspiration 
evaporates  as  fast  as  it  flows  out  through  the  pores,  if  the 
secretion  is  slow ;  but  if  poured  out  rapidly,  it  gathers  into 
drops  (Exp.  3).  The  perspiration  is  chiefly  water,  contain- 
ing in  solution  several  salts,  including 
common  salt  and  a  trace  of  a  white, 
crystalline  substance  called  urea.  The 
material  for  the  perspiration  is  fur- 
nished by  the  blood  flowing  around 
the  gland  in  a  network  of  fine  tubes. 
The  amount  of  the  perspiration  is  con- 
trolled in  two  ways :  by  nerves  that 
regulate  the  activity  of  the  epithelial 
cells  lining  the  gland,  and  by  nerves 
that  regulate  the  sice  of  the  blood  ves- 
sels supplying  the  gland  (Fig.  25). 

Thought  Questions.  —  Freckles,  Warts,  Moles,  Scars.  Proud  Flesh, 
Pimples.  Blackheads.     Use  these  names  in  the  proper  places  below  :  — 


Fig.  24.  —  Pores  on 
ridges  in  palm  of  hand. 


THE   SKIN  21 

A  rough  prominence  formed  by  several  papillae  growing  through  the 

epidermis  at  a  weak  spot  and  enlarging  is  called  a .     Small  patches 

of  pigment  developing  on  the  hands  and  face  from  much   exposure  to 

the  sun  are  called .       The  growth  of  exposed  dermis  sprouting 

through  an  opening  in  the  epidermis  due  to  accident  is  called . 

(This  should  be  scraped  off  and  cauterized  to  aid  the  epidermis  to  grow 
over  it  again.)  Sometimes  a  cut  heals  in  such  a  way  that  no  epidermis 
and  therefore  no  pigment  cells  cover  the  place  of  injury,  which  is  occu- 
pied only  by  white  fibrous  tissue  (cicatricial  tissue)   of  the  true  skin. 

In  this  case  the  mark  left  is  called  a  cicatrice  or  .     If  pores  or  the 

openings  of  oil  glands  become  clogged,  but  not  enlarged,  little  swell- 
ings called may  result.     An  enlarged  pore  filled  with  oil  and  dirt 

is  called  a .     A  spot  present  since  birth,  dark  with  pigment,  and 

often  containing  hairs  and  blood  vessels,  is  called  a  . 

Regulation  of  Temperature.  — As  is  well  known,  rapid 
running  or  violent  exercise  of  any  kind  causes  profuse  per- 
spiration. The  sweat  glands  are  connected  with  the  brain 
by  means  of  nerves,  and  when  the  body  has  too  much  heat, 
a  nerve  impulse  from  the  lowest  part  of  the  brain  causes  the 
sweat  glands  to  form  sweat  more  rapidly.  Heat  and  exer- 
cise may  cause  the  activity  of  the  sweat  glands  to  increase 
to  forty  times  the  usual  rate.  The  evaporation  of  the  sweat 
cools  the  body,  for  a  large  amount  of  heat  is  required  to 
evaporate  a  small  amount  of  water  (Exp.  4  and  5).  This 
is  shown  by  the  cooling  effect  of  sprinkling  water  on  the 
floor  on  a  warm  day.  By  fanning  we  hasten  the  cooling 
of  the  body  (Exp.  4). 

Exercise  tends  to  heat  the  body,  but  it  also  causes  us  to 
breathe  faster  and  causes  much  blood  to  flow  through  the 
skin.  Both  of  these  effects  aid  in  cooling  the  body,  for 
the  cool  air  is  drawn  into  the  lungs,  becomes  warm,  and 
takes  away  heat  when  it  leaves ;  and  the  warm  blood  flow- 
ing in  the  skin  loses  some  of  its  heat  to  the  cool  air  in  con- 
tact with  the  skin. 

Effects  of  Alcohol  upon  the  Skin.  —  The  more  blood 
goes  to  the  skin,  the  more  blood  is  cooled.      The  body 


22  HUMAN  BIOLOGY 

as  a  whole  may  be  cooler,  but  we  feel  wanner  when 
there  is  more  blood  in  the  skin  because  of  the  effect  of 
the  warm  blood  upon  the  nerves  of  temperature.  There 
are  no  nerves  for  perceiving  temperature  except  in  the 
skin  and  mucous  membrane,  and  the  body  has  practically 
no  sensation  of  heat  or  cold  except  from  the  skin  or 
mucous  membrane.  That  alcoholic  drinks  make  the  skin 
red  is  commonly  noticed.  Often  the  skin  is  flushed  by 
one  drink ;  the  bloodshot  eyes  and  purple  nose  of  the 
toper  are  the  results  of  habitual  use.  Can  you  explain 
why  alcohol  brings  a.  deceptive  feeling  of  warmth?  Why 
does  alcohol  increase  the  danger  of  freezing  during  ex- 
posure in  very  cold  weather  ?  During  the  chill  which  pre- 
cedes a  fever,  the  body  (except  the  skin)  is  really  warmer 
than  usual. 

Exercise  will  relieve  internal  congestion  and  send  the 
blood  to  the  skin  better  than  alcohol.  This  is  the  effect 
sought  by  sedentary  people  who  use  it  to  replace  exercise. 
The  long  and  sad  experience  of  the  race  with  alcohol 
proves  that  the  attempt  to  adapt  the  body  to  its  use  should 
be  given  up. 

Thought  Questions.  The  Functions  of  the  Skin.  —  1.  State  a  fact 
which  shows  that  the  skin  is  a  protection ;  gives  off  offensive  sub- 
stances ;  regulates  the  temperature.  2.  What  is  lacking  in  the  skin 
when  it  cracks  or  chaps?  Why  does  this  occur  more  often  in  cold 
weather?     When  the  hands  are  bathed  with  great  frequency? 

Effects  of  Indoor  and  Outdoor  Life.  —  Those  who  live  much  out  of 
doors,  exposed  to  sunlight  and  pure,  cold  air.  are  robust  and  hardy ; 
while  those  whose  occupations  keep  them  constantly  indoors,  especially 
if  no  physical  labor  is  necessary,  show  by  their  pale  skins,  their  fat  and 
flabby,  or  their  thin  and  emaciated  bodies,  the  weakening  effect  of  such 
a  life.  We  are  descended  from  ancestors  who  lived  in  the  open  air,  and 
it  is  impossible  for  a  human  being  to  live  much  indoors  without  de- 
generation of  the  body  and  shortening  of  life. 

A  Well-trained  Skin.  —  We  hear  a  great  deal  about  training  the 
muscles,  the  brain,  the  eye,  the  hand ;  yet  we  may  fail  to  realize  that 


THE   SKIN 


23 


<^-"i 


the  skin  also  can  be  trained  and  its  powers  developed,  or  it  can  be 
allowed  to  become  weak  and  powerless.  Soundness  of  the  skin  is  as  es- 
sential to  health  as  soundness  of  any  other  organ.  A  rosy  color  indicates 
good  health  because  of  a  well-balanced  circulation.  Paleness  often 
means  internal  congestion  and  great  liability  to  indigestion,  colds,  etc. 
Hence  we  think  a  rosy  skin  beautiful  and  a  pale  skin  ugly.  With  the 
skin  in  a  healthy  condition,  the  danger  of  taking  most  diseases  is 
removed. 

Characteristics  of  a  Vigorous  Skin.  —  A   person  who   readily  takes 
cold,  who  is  fearful  of  drafts  of  air  at  all  times,  has  a  weak  skin.     To 
one  who  has  a  healthy  skin  drafts  are  dangerous  only  when  the  skin 
is  moist  with  perspira- 
tion, and   the  bodv  is  *? 
inactive ;     cold    drafts 
may    then    do    harm. 
Cold  air  and  cold  water 
are  the  best  means  of 
toughening     a     tender 
skin.      A  batJi  is  to  the 
skin    what    gymnastic 
exercises     are    to     the 
muscles.     The    muscle 
fibers    in    the  walls  of 
the  blood  vessels  and 
the  nerves  controlling  e#i=^^ 
them  need  exercise  as 
well  as  the  rest  of  the 
body  (Fig.  25). 

Importance  of 
Bathing.  —  If  we 
followed  the  out- 
door life  and  wore 
the  scanty  clothing  of  savage  races,  the  rains,  the  cool  air, 
and  the  sunlight  would  keep  our  skins  vigorous  and 
sound.  But  want  of  exercise  to  induce  perspiration  allows 
the  sweat  glands  to  become  stopped  up.  The  wearing 
of  clothes  is  a  very  uncleanly  custom.  Clothes  make  the 
skin  inactive,  yet  confine  the  impurities  which  the 
weakened  skin  may  still  be  able  to  excrete.     Thick  and 


Fig.  25.  — Blood  Vessels,  with  the  Vaso-motor 
Nerves  which  accompany  and  control  them. 


24  HUMAN  BIOLOGY 

heavy  clothing  and  overheated  rooms  prevent  the  nerves 
from  being  stimulated  by  cold  air  and  sunlight.  The  best 
way  to  counteract  these  weakening  conditions  is  by  frequent 
cool  or  cold  baths.  An  air  bath,  which  consists  of  exposing 
the  bare  skin  to  the  air  for  half  an  hour  or  more  before 
dressing  in  the  morning,  may  take  the  place  of  a  cold 
bath.  Even  the  lower  animals  bathe :  birds,  dogs,  and 
many  lower  animals  bathe  in  the  rivers.  An  elephant 
sometimes  takes  a  bath  by  showering  water  over  his  back 
with  his  trunk. 

Treatment  of  Burns.  —  Wet  the  burn  with  a  little  water 
and  sprinkle  common  baking  soda  or  flour  thickly  on  it. 
Bind  with  a  narrow  bandage.  For  deeper  burns  soak  a 
small  square  of  cloth  in  a  strong  solution  of  baking  soda, 
bandage  it  on  wound,  and  keep  it  wet  with  the  solution. 
Olive,  cotton  seed,  and  linseed  oils  are  excellent  for  burns 
(Exp.  13). 

Hygiene  of  Bathing.  —  A  bath  should  not  be  taken 
within  an  hour  after  a  meal.  Cold  baths  (1)  should 
never  be  taken  in  a  cold  room  nor  when  the  skin  is 
cold ;  (2)  are  more  beneficial  in  summer  and  in  warm  cli- 
mates, but  are  necessary  in  winter  for  those  who  live  in 
overheated  houses  or  dress  very  warmly ;  (3)  should  be 
followed  in  winter  by  vigorous  rubbing  and  a  glowing  re- 
action ;  (4)  should  usually  not  last  longer  than  one  minute 
in  winter.  Warm  baths  (1)  are  more  cleansing  than  cold 
baths ;  (2)  should  not  be  used  alone  but  should  always  be 
followed  by  a  dash  of  cold  water  ;  (3)  are  better  than  cold 
baths  if  the  body  is  greatly  fatigued  ;  (4)  are  more  benefi- 
cial when  going  to  bed  than  upon  rising. 

Cold  baths  and  very  hot  baths  are  both  stimulants  to 
the  nervous  system  and  cause  an  expenditure  of  nervous 
energy.     For  one  whose  nervous  energy  is  at  a  very  low 


THE  SKIN  25 

ebb  cold  baths  may  be  weakening  if  prolonged  beyond  a 
few  seconds.  For  one  with  skin  relaxed  and  body  sluggish 
from  indoor  life,  cool  baths  arouse  activity,  tone  up  the 
body,  and  may  be  as  beneficial  as  outdoor  exercise  in  restor- 
ing vigorous  health.  As  with  every  hygienic  measure, 
each  person  must  find  out  by  experience  what  suits  him 
best. 

Clothing  was  first  employed  for  ornament.  In  cold  climates  it  aids 
in  maintaining  the  uniform  temperature  of  the  body ;  to  it  man  owes 
his  distinction  of  being  the  most  widely  distributed  of  animal  species. 
Clothing  prevents  rapid  escape  of  bodily  heat  by  confining  air,  a  non- 
conductor of  heat,  in  its  meshes.  Hence,  the  effect  of  clothing  varies 
with  the  weave;  likewise  with  the  tendency  of  its  fibers  to  keep  dry,  for 
if  water  replaces  air  in  the  meshes,  the  body  loses  heat  rapidly.  For 
cool  clothing  the  weave  should  be  hard  and  tight,  for  warm  clothing  it 
should  be  soft  and  loose.  The  warmth  of  clothing  is  affected  more  by 
its  weave  than  by  its  weight.  The  weave  may  be  tested  by  stretching ; 
the  fabric  with  softest  weave  will  stretch  the  most  (Exp.  8).  Linen 
makes  the  coolest  of  all  clothing  because  it  weaves  hard  with  small 
meshes ;  silk  ranks  next  in  coolness.  When  warmth  is  desired,  linen 
or  cotton  garments  should  be  made  of  fabrics  woven  like  stockings. 
Linen  and  cotton  both  absorb  water  rapidly  and  dry  rapidly  (Exp.  6)  ; 
if  woolen  did  also,  it  would  make  the  warmest  of  all  clothing,  but  it 
dries  so  slowly  (Exp.  7)  that  it  cools  the  body  after  the  activity  is  over 
instead  of  drying  rapidly  and,  as  with  linen  and  cotton,  keeping  the 
body  cool  during  the  exertion  (Exp.  o).  Woolen  weaves  with  the 
largest  air  meshes  of  all  materials :  hence  its  warmth  increases  perspi- 
ration, but  woolen  removes  perspiration  most  slowly"  and  tends  to  relax 
the  skin  if  the  wearer  has  an  active  skin  or  makes  active  exertion. 
Woolen  is  best  for  underclothing  during  extreme  cold  only  or  for  per- 
sons who  never  make  such  vigorous  muscular  exertion  as  to  perspire. 
In  general,  cotton  or  linen  is  best  for  underwear.  They  possess  the 
added  advantages  of  less  cost  and  of  not  shrinking  out  of  size  and 
shape  when  washed.  A  mixture  of  cotton  and  silk  or  of  cotton  and 
wool  is  more  durable  than  either  alone.  Cotton  and  linen,  unlike 
woolen,  are  not  attacked  by  insect  pests. 

It  is  better  to  depend  more  upon  outer  clothing  than  underclothing 
for  warmth.  In  the  Gulf  states  the  wearing  of  woolen  outer  clothing 
indoors  during  warm  weather  (which  lasts  eight  months)  is  unhealth- 
ful  and  uncleanly  because  of  the  perspiration  absorbed ;    this  is  as 


26 


II UMAX  BIOLOGY 


absurd  as  to  wear  cotton  outer  clothing  in  Northern  states  during  the 
eight  cold  months. 

Black  clothing  absorbs  twice,  blue  aimost  twice,  red  and  yellow 
almost  one  and  a  half  times,  as  much  heat  as  white  clothing  (Exp.  10). 
Which  material  protects  best  from  radiant  heat  ?  (Exp.  9.)  Because 
large  blood  vessels  are  near  the  surface  at  the  neck,  wrists,  and  ankles 
very  thin  or  no  covering  at  those  points  aids  greatly  in  keeping  the 
body  cool.  High  collars,  long  sleeves,  and  high  shoes  are  unhealth- 
ful  in  warm  climates  and  in  summer.  What  objection  to  black  shoes 
in  summer  ?  Patent  leather  ?  Show  how  women  dress  more  sensibly 
in  hot  weather  than  men. 

The  kidneys  are  located  on  each  side  of  the  spinal  col- 
umn in  the  "  small  of  the  back  "  and  extend  slightly  above 

the  level  of  the  waist. 
They  are  bcan-sJiaped  or- 
gans about  four  indies  long 
(Fig.  26).  The  kidneys  of 
a  sheep  or  ox  closely  re- 
semble those  of  man.  They 
are  outside  of  the  perito- 
neum (Fig.  99)  and  at- 
tached to  the  rear  wall  of. 
the  abdomen.  A  large 
artery  (12,  colored  Fig.  5) 
goes  to  each  kidney  and 
divides  into  many  capilla- 
ries which  surround  tubules 
in  the  kidneys  (Fig.  27). 
The  secretion,  containing 
nitrogenous  impurities  of 
the  blood,  is  continually  being  deposited  in  the  tubules, 
which  take  it  to  a  funnel-shaped  cavity  at  the  inner  edge 
of  the  kidney  (Fig.  26).  From  this  cavity  a  white  tube 
called  the  ureter  leads  down  to  a  storage  organ  in  the 
pelvis  called  the  bladder. 


Fig.  26. —  Section  of  Kidney. 

RA,  renal  artery;  Py,  pyramids  surrounding 
hollow  space  from  which  the  ureter  (£/) 
leads  the  secretion  to  the  bladder. 


THE   SKIN 


27 


Fig.  27.  —  Plan  of  a 
Urinary  Tubule, 
Tb,  with  artery  A, 
and  V  in  /  V. 


Changes  in  Blood  in  the  Kidneys.  — 
The  water  holding  the  nitrogenous 
waste  varies  in  amount  with  the 
amount  of  water  drunk  and  with  the 
activity  of  the  skin,  being  less  in  sum- 
mer when  the  perspiration  is  great. 
The  lungs  aid  the  skin  and  kidneys 
in  disposing  of  superfluous  moisture. 
The  kidneys  have  almost  the  entire 
responsibility  of  relieving  the  body  of 
certain  mineral  salts  and  a  white  crys- 
talline solid  called  urea.  This  is  very 
injurious  if  retained,  causing  headaches,  rheumatism,  and 
other  troubles. 

Thought  Questions.  Hygiene  of  the  Skin.  —  1.  What  kind  of  a 
scar  is  not  affected  by  freckles  or  tan?  2.  Can  a  scar  on  a  negro  be 
white?  3.  Does  a  scar  on  a  child  grow  in  size?  4.  Why  is  heat 
most  oppressive  in  moist  weather?  5.  How  do  you  account  for  the 
shape  and  location  of  the  usual  bald  spot?  6.  How  does  the  wearing 
away  of  the  outer  cells  of  the  epidermis  contribute  to  the  cleanliness  of 
the  body?  7.  Why  does  the  palm  of  the  hand  absorb  water  more 
rapidly  than  the  back  of  the  hand?  8.  Is  it  more  necessary  for  mental 
workers  to  bathe  often  or  change  their  clothes  often?  For  physical 
workers?  9.  Is  cotton  or  woolen  clothing  more  liable  to  stretch  or 
shrink  out  of  shape  or  size  ?  To,  catch  fire?  To  make  the  skin  clammy 
with  moisture  ?     To  cost  more  ?     To  be  eaten  by  moths  ? 


Os  Jrontale 

Maxilla  superior 
Maxilla  inferior 
Clavkula 

Humerus 


Os  parietale 
Os  temporale 
Os  occipitis 

Vertebrae 


Tibula 


Tarsus 
Digiti  pedis 


Fig.  28.  —  The  Skeleton. 
28 


CHAPTER    III 

THE   SKELETON 

Experiment  i.  (At  home.)  Is  the  Arch  of  the  Foot  Elastic?  — 
Wet  the  foot  in  a  basin  of  water  and.  while  sitting,  place  the  foot  flat 
upon  a  piece  of  paper.  Draw  the  outline  of  the  track.  Repeat,  but 
stand  with  your  whole  weight  upon  the  foot.  Draw  track.  Con- 
clusion? (Take  sketches  to  school.  Which  sketch  shows  the  flattest 
foot?)  Devise  a  method  for  measuring  the  length  of  the  foot  with 
and  without  the  weight  of  the  body  upon  it.  What  difference?  Con- 
clusion ? 

Experiment  2.  Composition  of  Bone.  —  Place  a  bone  in  a  hot  fire  and 
let  it  remain  for  three  or  four  hours.  It  will  keep  its  shape  however  long 
you  burn  it :  but  unless  you  handle  it  carefully  when  you  take  it  out,  it 
will  crumble  to  pieces.  If  not  thoroughly  burned,  the  bone  will  be 
black  from  the  carbon  of  the  animal  matter  still  left  in  it.  Experiment  3. 
Obtain  a  slender  bone  like  the  rib  of  a  hog  or  the  leg  bone  of  a  fowl, 
and  put  the  raw  bone  into  a  vessel  containing  strong  vinegar  or  two 
ounces  of  muriatic  acid  and  a  pint  of  water.  Leave  it  there  for  four 
days.  When  the  bone  is  taken  out,  it  can  be  tied  into  a  knot.  The 
acid  may  be  washed  off.  and  the  bone  preserved  in  a  bottle  of  alcohol 
or  glycerine. 

Experiment  4.  The  Forms  of  Joints.  —  Obtain  the  disjointed  bones 
of  a  fowl  or  small  mammal  and  place  them  one  at  a  time  in  their 
sockets  and  study  the  fit  and  motion  of  the  joints. 

Experiment  5.  Pivot  Joints.  —  Through  what  fraction  of  a  circle  do 
the  pivot  joints  in  the  forearm  and  neck  allow  the  hand  and  head  to 
rotate? 

Review  Questions. — Where  are  the  bone  cells?  How  does  nour- 
ishment reach  them?  How  has  the  mineral  part  of  the  bones  been  de- 
posited? How  long  may  bone  cells  live?  Name  animals  with  outside 
skeletons.     Inside  skeletons.     No  skeleton. 

Forms  and  Uses  of  Bones.  —  The  three  chief  uses  of  bones 
arc  protection,  motion,  and  support.  In  order  to  fulfill 
these  purposes,  the  bones  must  have  different  sizes,  shapes, 
and  positions.     The  bones  are  classed  by  shape,  as  long, 

-1 


3o 


HUMAN  BIOLOGY 


— C  Marrow. 


flat,  and  irregular.     Those  whose  chief  use  is  to  protect  arc 
broad  and  flat.     The  bones  which  furnish  support  arc  thick 

and  solid ;    those  designed  to   aid  in 
motion  arc  long  and  straight.    Including 
six  small  bones  in  the  ear,  there  are  two 
hundred   and   six  bones      E 
in  the  adult  skeleton. 

Gross  Structure  of 
Bones.  —  The  structure  ti\  v 
of  a  long  bone  is  shown  V^f 
in  Fig.  29.  It  has  a 
long,  Jwllorv  shaft  of 
hard,  compact  bone,  and 
enlarged  ends  composed 
of  spongy  bone.  The 
hollow  in  the  shaft  is 
filled  with  yellow  mar- 
row, which  is  composed 
of  blood  vessels  and  fat, 
and  aids  in  nourishing 
the  bone.  The  long  bones 
are  found  in  the  limbs 
(Fig.  28).  The  ribs  and 
other  flat  bones  and  the 
irregular  bones  contain 
no  yellow  marrow  ;  they 


Com  pad 
•A  or  dense 


Fig.  30.  — 


Fig.  29.  —  Femur,  sawed 
lengthwise.  The  red 
blood  cells  are  formed 

in  the  red  marrow  of   are  spongy   inside,  and 
the  spongy  part.  hard  and  compact  near 

the  surface.     There  is  a  red  marrow  in  the  front  view  of 

ri  .„.  N       Right  Femur. 

cavities  in  the  spongy  parts  of  bones  {rig.  29). 

Neiv  red  blood  cells  arc  formed  in  this  marrow.  The  bones 
have  a  close-clinging,  fibrous  covering  composed  of  con- 
nective tissue  and  blood  vessels.      It  is  called  periosteum. 


THE   SKELETON 


31 


Chemical  Composition  of  Bone.  —  Experiments  (2  and  3) 
show  that  the  bones  contain  a  mineral  or  earthy  substance, 
which  makes  them  hard  and  stiff,  and  ~ 
a  certain  amount  of  animal  matter, 
called  gelatine,  which  binds  the  min- 
eral matter  together  and  makes  the 
bones  tough  and  somewhat  elastic. 
The  fire  burned  out  the  animal  matter  rj, 
of  the  first  bone,  and  the  acid  dissolved 
out  the  mineral  matter  of  the  second 
bone.  The  mineral  matter  is  chiefly 
lime,  and  makes  up  about  two  thirds  of 
the  weight  of  the  bone.  (Why  is  more 
mineral  than  animal  matter  needed  ?) 
The  animal  gelatine  is  a  gristly  sub- 
stance. As  the  body  grows  old,  the 
animal  matter  of  the  bones  decreases, 
and  they  become  lighter.  They  are  [_. 
more  easily  broken  and  do  not  heal  so 
readily  as  the  bones  of  young  persons. 

The  skeleton  is  subdivided  into  the 
bones  of  the  head,  trunk,  and  limbs. 
The  bones  of  the  trunk  are  those  of 
the  spine,  the  chest,  the  shoulder  blades, 
collar  bone,  and  hip  bones. 

The  spinal  or  vertebral  column  is 
made  up  of  twenty-six  bones  (Fig.  31). 
It  is  the  axis  of  the  human  skeleton, 
to  which  all  other  bones  are  directly 
or  indirectly  attached.  Animals  with 
inside  skeletons  have  this  column,  and 
are  called  vertebrates.  Fish,  reptiles,  birds,  beasts,  apes, 
and  man  are  vertebrates.    The  spine,  as  this  column  is  some- 


G-..5 


Fig.  31.  —  Vertebral 
Column.    Side  view. 


J/ I'M  AX  BIOLOGY 


times  called,  is  not  only  the  main  connecting  structure  and 
support  of  the  body,  but  it  forms  a  channel  through  which 
passes  the  spinal  cord. 

Fig.  32  shows  a  vertebra,  or  one  of  the  bones  that  compose  the 
column.     The  three  projecting  points  or  processes  are  for  the  attachment 

of  ligaments  and  muscles.  The  main  body 
of  each  vertebra  is  for  supporting  the 
weight  transmitted  by  the  column  above. 
Just  behind  this  thick  body  is  a  half  ring 
(Fig.  32),  which  with  the  half  rings  on 
the  other  vertebrae  form  the  channel  for 
the  spinal  cord.  Between  the  vertebrae 
are  thick  pads  of  gristle,  or  cartilage,  which 
act  as  cushions  to  prevent  jars,  and  by 
compression  allow  bending  of  the  spinal 
column  in  all  directions. 

The  Chest  (see  Fig.  75). — The 

twelve  pairs  of  ribs  are  attached 

fig.  32. —  Side  and  under     to  the  spinal  column  behind,  and 

View  of  a  Vertebra.  .  ,  .  ,  .,       ,  , 

extend  around  toward  the  front  of 

the  body,   somewhat   like  hoops.     The  first  seven  pairs, 

called  true  ribs,  are  attached  directly  to  the  flat  breastbone, 

or  sternum.     Each  of  the  next  three  pairs,  called  false  ribs, 

is   attached   to  the   pair    above   it.      The   last   two    pairs. 

called  floating  ribs,  are  free  in  front. 

The  Shoulder  Girdle.  —  The  collar  bones  (Fig.  28)  can  be 
traced  from  the  shoulders  until  they  nearly  meet  on  the 
breastbone  at  the  top  of  the  chest.  The  collar  bone  is 
shaped  like  the  italic  letter/;  it  helps  to  form  the  shoulder 
joint  and  holds  the  shoulder  blade  out  from  the  chest  that 
the  motions  of  the  arm  may  be  free. 

The  flat,  triangular  shoulder  blade  (Fig.  75)  can  be  felt 
by  reaching  with  the  right  hand  over  the  left  shoulder.  It 
spreads  over  the  ribs  like  a  fan.  Its  edges  can  be  made 
out,  especially  if  the  shoulder  is  moved  while  it  is  being 


THE   SKELETON 


33 


Parietal 


Elhmniil 


Occipital 


Fig.  33.  —  Human  Skull, 
disjointed. 


felt.     The  high  ridge  which  runs  across  the  bone  can  be 
felt  extending  to  the  top  of  the  shoulder. 

The  Pelvic  Girdle.  —  The  edges  of  the  hip  bones  can  be 
felt  at  the  sides  of  the  hips  (Fig.  28).  The  hip  bones, 
with  the  base  of  the  spine, 
form  a  kind  of  basin  called 
the  pelvis. 

The  skull  (Fig.  33)  rocks, 
or  nods,  on  the  top  vertebra. 
It  consists  of  the  cranium,  or 
brain  case,  and  the  bones  of 
the  face.  The  shapes  and 
names  of  the  bones  of  the 
skull  are  shown  in  Fig.  33. 

Adaptations  of  the  Skull 
for  Protection.  —  Its  arched 
form  is  best  for  resisting  pressure  and  turning  aside  blows. 
Like  all  flat  bones,  the  skull  has  a  spongy  layer  of  bone 
between  the  layers  of  compact  bone  forming  the  outer  and 
inner  surfaces ;  hence  it  is  elastic  and  not  easily  cracked. 
The  nose,  brow,  and  cheek  bones  project  around  the  eye 
for  its  protection.  The  delicate  portions  of  the  ear  are 
embedded  in  the  strongest  portion  of  the  skull.  The 
branches  of  the  nerves  of  smell  end  in  the  lining  of  the 
bony  nasal  chambers.  The  spinal  cord  rests  securely  in 
the  spinal  canal. 

The  arms  and  legs  have  bones  that  closely  correspond  to 
each  other.  The  Latin  names  of  these  bones,  as  well  as 
of  all  the  other  bones,  are  given  in  Fig.  28.  There  are 
30  bones  in  each  arm  and  30  in  each  leg  (Fig.  34). 
Here  is  a  list  of  the  bones  of  the  arm,  followed  by  the 
names  in  brackets  of  the  corresponding  leg  bones  :  upper 
arm  bone  [thigh  bone],  2  forearm  bones  [shin  bone  and 


34 


HUMAN  lUOr.OGY 


splint  bone],  8  wrist  bones  [7  ankle  bones],  5  palm  bones 
[5  bones  of  instep],  14  finger  bones  [14  toe  bones].  The 
shin  bone  is  the  larger  bone  between  knee  and  ankle. 
The  long,  slender  splint  bone  and  the 
shin  bone  are  bound  side  by  side. 

Differences  between  Arm  and  Leg.  — 
There  is  a  saucer-like  bone,  called  the 
kneecap,  embedded  in  the  large  liga- 
ment which  passes  over  each  knee. 
There  is  no  such  bone  in  the  elbow. 
There  is  one  less  bone  in  the  ankle 
than  in  the  wrist,  hence  there  are  the 
same  number  of  bones  in  the  arm  and 
leg.  The  shoulder  joint  is  more  freely 
movable  than  the  hip  joint.  The  fin- 
gers are  longer  and  more  movable  than 
the  toes;  the  thumb  moves  far  more 
freely  than  the  big  toe.  The  instep  is 
much  stronger  than  the  palm  ;  for  each 
instep  must  support,  unaided,  the 
weight  of  the  whole  body  at  each  step, 
with  any  other  weight  that  the  person 
may  be  carrying.  The  palm  is  nearly 
flat,  but  the  instep  is  arched  to  prevent 
jars.  When  the  weight  of  the  body  is 
thrown  on  the  foot  at  each  step,  the  top  of  the  arch  is 
pressed  downward,  making  the  foot  longer  than  before. 
The  arch  springs  up  when  the  weight  is  removed  (Exp.  1). 

Illustrated  Study.  The  Shapes  of  Bones.  —  Write  L7  F,  or  / 
after  these  names  (see  Fig.  28,  etc.).  according  as  the  bones  are  long, 
flat,  or  irregular :  face,  cranium,  vertebra,  hip.  rib,  breast- 
bone, collar  bone,  shoulder  blade,  upper  arm  bone,  lower 
arm  bones,  wrist,  palm,  fingers,  thigh  bone,  shin  bone, 
splint  bone,       ankle,       instep,       toes,       kneecap. 


Fig.  34.  —  Bones  of 
Arm  and  Leg. 


THE  SKELETON  35 

Structure  of  Joints. — The  meeting  of  two  bones  forms 
a  joint  (Exp.  4).  Some  of  the  joints  are  immovable. 
The  skull  bones  join  in  zigzag  lines  called  sutures,  formed 
by  the  interlocking  of  sawlike  projections  (Fig.  35).  These 
immovable  joints  are  necessary  for  the  protection  of  the 
brain,  which  is  the  most  delicate  of  the  organs.     The  brain 

attains  almost  its  full  size  by  the  seventh       , 

year  of  life;  its  bony  case  needs  to  grow       ;  yu^v^ 
very  little  after  that.      The  joints  of  the       :  i§^  .-' 
pelvis    are  also  immovable.     All  movable      :   *^v,    .■ 
joints  have  two  cartilages,  and  as  the  bones  "^r^-v 

turn,   one   cartilage   slips   over  the  other.  «a 

There  is   an   intermediate  class  of   joints       •    ^SpS 
found  between  the  vertebrae  and  where  the       t      /^D. 
ribs  join  the  breastbone.     These  joints  de-  FlG.  35._ sutures 
pend  for  their  motion  upon  the  flexibility         OF  Skull- 
and  compressibility  of  their  cartilages.     They  are  called 
mixed,  or  elastic,  joints,  and  allow  slight  motion.     Such  a 
joint  has  only  one  cartilage. 

Kinds  of  Movable  Joints.  — The  movable  joints  are  found 
chiefly  in  the  limbs.  When  one  end  of  the  bone  is  rounded 
and  fits  into  a  cuplike  hollow,  the  joint  allows  motion  in 
all  directions,  and  is  known  as  a  ball-and-socket  joint.  The 
hip  joints  and  shoulder  joints  are  examples.  A  hinge  joint 
allows  motion  in  only  two  (opposite)  directions ;  for  exam- 
ple, the  to-and-fro  motion  of  the  elbow.  A  pivot  joint 
allows  a  rotary  motion ;  examples,  the  first  vertebra  on 
the  second,  one  bone  of  forearm  upon  the  other.  A  glid- 
ing joint  consists  of  several  bones  that  slide  upon  one 
another,  as  at  the  wrists  and  ankles. 

The  Four  Features  presented  by  a  Movable  Joint  (Fig. 
36).  —  If  not  held  in  place,  the  bones  would  slip  out  of 
their  sockets,  hence  there  are  ligaments,  or  tough  bands, 


36 


HUMAN  BIOLOGY 


to  bind  the  bones  together.     Sudden  jolts  would  jar  the 
bones  and  injure  them;  shocks  are  prevented  by  a  layer 

of  elastic  cartilage  over  the 
end  of  each  bone.  The  mov- 
ing of  one  bone  over  another 
in  bending  a  joint  would  wear 
the  bone  with  friction  un- 
less the  cartilages  were  very 
smooth  and  lubricated  with  a 
fluid  called  the  synovial  fluid. 
The  synovial  fluid  would  be 
constantly  escaping  into  the 
surrounding  tissues  except  for 
the  collarlike  ligament  called 


\JM Synovial 

membrane 


Fig.  36. —  Diagram  of  a  Joint. 


the  capsule,  which  surrounds  the  joint  and  is  attached  to 
each  bone  entirely  around  the  joint  (Fig.  36). 

Thought  Questions.     The  Kinds  of  Joints. — Write  B,  H,  G.  E, 
P,  or  /after  these  names  according  to  the  kind  of  joint  (ball-and-socket, 
hinge,  gliding,  elastic,  pivot,  immovable)  :  between  bones  of  skull, 
head  nodding,         head  turning.         vertebrae,         lower  jaw,         ribs  to 
breastbone  (Fig.  75),        shoulder,        elbow,        wrist,         fingers, 
hip,         knee,         ankle,         toes. 

Growth  of  Bones.  —  The  blood  vessels  pass  into  the  bones  from  the 
periosteum.  If  the  periosteum  is  removed^  the  larger  blood  vessels  are 
taken  aivay  and  the  bone  beneath  it  perishes.  If  the  underlying  bone  is 
removed  and  the  periosteum  left,  the  bone  will  be  replaced.  A  curious 
proof  of  the  active  circulation  in  the  bone  is  furnished  when  madder  is 
mixed  with  the  food  of  pigs.  In  a  few  hours  the  bones  become  a  darker 
pink  than  usual ;  and  if  the  madder  is  fed  to  the  pigs  for  a  few  days, 
their  bones  become  red.  A  child  grows  in  height  chiefly  during  three 
or  four  months  in  spring  and  summer ;  but  its  body  broadens  and 
becomes  heavier  during  autumn. 

Health  of  the  Bones.  —  It  is  plain  that  a  strong  and  free  circulation 
of  pure  blood  contributes  to  the  health  and  strength  of  the  bones  ;  good 
food  and  pure  air  make  pure  blood.  Cases  of  "  delayed  union,"  or 
slow  mending  of  broken  bones,  occur  more  often  with  intemperate  than 
with  sober  people.     This  is  because  the  vitality  of  the  bone  cells  has 


THE   SKELETON 


37 


V*t 


been  weakened  by  the  use  of  alcohol.    Many  surgeons  dislike  to  operate 
on  an  old  drunkard. 

Posterior  Curvature  of  the  Spine.  — The  spine  (see  Figs.  28,  31)  has 
two  backward  curves  (opposite  chest  and  hips)  and  two  forward  curves 
(at  loins  and  neck).  The  deformity  called  posterior  curvature  is  chiefly 
an  exaggeration  of  the  upper  posterior  curve.  Round  shoulders  is  the 
slightest,  and  hunchback  the  most  marked,  degree  of  this 
deformity.  Causes  :  I,  bending  over  the  work  while  either 
standing  or  sitting  ;  2,  slipping  down  in  the  seat,  as  in  Fig- 
ure 51  ;  3,  working  habitually  with  the  work  low  in  front, 
as  reading  and  writing  at  too  low  a  desk  (Fig.  49),  or  bend- 
ing over  while  hoeing,  sitting  on  the  floor  (Japanese  and 
Chinese)  ;  4,  weak  muscles  in  the  back  ;  5,  wearing  shoes 
with  high  heels ;  6,  binding  the  ribs  down  with  tight  cloth- 
ing; 7,  walking  with  the  head  drooped  forward  or  the 
chest  flat ;  8,  wearing  suspenders  without  a  pulley,  or  lever, 
at  the  back  ;  9,  carrying  the  hands  in  the  pockets.  (Swing 
the  arms  to  keep  the  hands  out  of  the  pockets  and  break 
the  habit)  ;  10,  wearing  a  coat  or  vest  that  is  tight  at 
the  back  of  the  neck.  This  deformity  is  brought  about  by 
stretching  the  ligaments  at  the  back  side  of  the  spine,  and 
by  compressing  the  cartilages  until  they  become  wedge- 
shaped,  with  the  thin  part  of  the  wedge  in  front.  The 
flexibility  of  the  spine  is  a  great  advantage,  but  it  in- 
creases the  risk  of  deformity.  One  of  the  most  serious 
evils  of  posterior  curvature  is  a  flat  chest  and  restricted 
breathing. 

Lateral  Curvature  of  the  Spine.  —  A  perfect  spine  curves 
to  neither  side  (Fig.  47),  but  is  perfectly  erect.  The  least 
habitual  lateral  curvature  is  deformity.  Causes:  1,  writing 
at  a  desk  that  is  too  high  ;  2,  habitually  carrying  a  book, 
satchel,  or  other  weight  in  the  same  hand;  3,  carrying  the 
head  on  one  side  (Fig.  46)  ;  4,  habitually  standing  with  the 
weight  on  the  same  foot ;  5,  a  certain  defect  of  vision 
(astigmatism.  Chap.  IX). 

To  overcome  Spinal  Deformities.  —  The  work,  or  the 
manner  of  doing  the  work,  should  be  so  changed  as  to  give 
extra  labor  to  the  neglected  muscles.  Avoid  the  habits 
mentioned  above  as  causing  deformitv.     Sit  and  stand  in  38- — 

C~*  O  R  R  F"  C  T 

the  manner  described  in  the  next  paragraph.     Sleeping  on     POSTURF 
the  back  upon  a  hard  mattress  without  a  pillow  tends  to     ^ut  strained 
cure  posterior  curvature  and  flat  chest.  and  stiff. 


Fig.  37.  — 
Incorrect 
posture. 


M 


38 


Ili'MAX  BIOLOGY 


The  correct  position  in  standing  is  :  chest  forward,  chin  in,  hips  back 
(Figs.  38,  39).  To  sit  correctly,  sit  far  back  in  the  chair  (Ki.Lis.  60, 
61,  62)  with  the  body  erect  and  balanced.  In  youth  the  bones  are  soft 
and  growing;  they  will  readily  grow  into  perfect  shape,  and  will  almost 
as  readily  grow  deformed. 

Sprains.  —  Immerse  the  part  in  hot  water  for  half  an  hour,  then 
bandage  to  keep  the  part  at  rest.  Use  the  limb  as  little  as  possible.  It 
may  be  necessary  for  a  physician  to  apply  a  plaster  dressing  to  a  very 
bad  sprain  where  the  ligament  is  torn  from  the  bone. 

Broken  Bones.  —  To  prevent  bone  from  cutting  flesh  and  skin,  do  not 
move  the  person  until  a  temporary  splint  has  been  provided  by  tying 
sticks  or  umbrellas  around  the  limb  with  handkerchiefs. 

Practical  Questions.  The  Skeleton. — 1.  What  kind  of  a  chair 
back  causes  one  to  slide  forward  in  the  seat?  2.  What  fault  in  sitting 
is  made  necessary  by  using  a  chair  with  so  large  a  seat  that  the  front 
edge  strikes  the  occupant  behind  the 
knee?     3.    Why  is  the  shoulder  more 


often  dislocated  than 
the  hip?  4.  High  pil- 
lows may  cause  what 
deformity?  5.  Find 
three  bones  in  the 
body  not  attached  to 
other  bones.  Find 
twenty-five  bones  at- 
tached to  other  bones 
by  one  end  only  (Figs. 
28  and  39).  6.  What 
deformities  may  result 
from  urging  a  young 
child  to  stand  or  walk  ? 
7.  Which  bone  is 
most  often  broken  by 
falling  upon  the  shoul- 
der? 8.  Where  in 
bones  is  fat  stored  for 
ilc.  39.— The  Human  Skeleton  in  Action.  future  use?  9.  Liga- 
ments grow  very  slowly.     Why  is  recovery  from  a  sprain  often  tedious? 


CHAPTER    IV 
THE  MUSCLES 

It  has  already  been  stated  that  there  are  at  least  two 
muscles  attached  to  a  bone  to  move  it  in  opposite  direc- 
tions. Since  there  are  two  hundred  and  six  bones,  you 
are  not  surprised  to  learn  that  to  move  the  bones  and 
accomplish  the  various  purposes  just  stated,  there  are 
five  hundred  and  twenty-six  (526)  skeletal  muscles. 

Two  Kinds  of  Muscles.  —  All  muscles  are  controlled  by 
means  of  the  nervous  system.  Some  of  them  are  directed 
by  parts  of  the  brain  that  work  consciously;  others  are 
controlled  by  the  spinal  cord  and  the  parts  of  the  brain 
that  work  unconsciously.  Those  of  the  first  kind  are 
usually  controlled  by  the  will,  but  they  sometimes  act  invol- 
untarily. They  are  called  voluntary  muscles.  They  move 
the  bones  and  are  located  in  the  limbs  and  near  the  surface 
of  the  trunk  (Fig.  44).  The  other  kind  of  muscles  are 
never  controlled  by  the  will,  and  are  called  involuntary 
muscles.  We  cannot  cause  them  to  act,  nor  can  we  prevent 
them  from  acting.  They  contract  more  slowly  than  the 
voluntary  muscles.  Most  of  them  are  tubular  and  found 
in  the  cavity  of  the  trunk.  The  involuntary  muscles  belong 
to  the  internal  organs,  and  relieve  the  will  of  the  responsi- 
bility and  trouble  of  the  activity  of  these  organs  ;  other- 
wise, the  mind  would  have  no  time  for  voluntary  actions. 

Gross  Structure  of  Voluntary  Muscles. — A  beefsteak  is 
seen  to  be  chiefly  red,  although  parts  of  it  are  white  or 
yellowish.     The  white  or  yellowish  flesh  is  fat ;  the  red, 

39 


40 


HUMAN  BIOLOGY 


Fig.  40.  —  Muscle  Bundles  bound  to 
gether  by  connective  tissue  sheaths. 


lean  flesh  is  voluntary 
muscle.  If  a  piece  of  beef 
is  thoroughly  boiled,  it 
may  be  easily  separated 
into  bundles  the  size  of 
large  cords.  These  bun- 
dles may,  by  the  use  of 
needles,  be  picked  apart 
and  separated  into  thread- 
like fibers  (Fig.  40). 
Microscopic  Structure  of  Muscles. — These  threadlike 
fibers  may,  under  a  magnifying  glass, 
be  separated  into  fine  strands  called 
fibrils.  These  last  arc  the  true  muscle 
cells ;  they  are  shown  by  the  micro- 
scope to  be  crossed  by  many  dark  lines 
(Fig.  48).  Hence  voluntary  muscles  are 
called  striated  or  striped  muscles.  Pro- 
longed boiling  and  patient  picking  with 
a  needle  are  needed  to  dissect  muscle, 
because  the  bundles  are  held  together 
by  thin,  glistening  sheets  of  connective 
tissue  by  which  they  are  surrounded. 
This  connective  tissue  surrounds  and 
holds  in  place  the  separate  fibers  of  each  bundle  (Fig.  40). 

The  fibrils  of  invol- 
untary muscles  are 
swindle -shaped  (see 
Fig.  42).  There  are  no 
cross  lines  on  the  fibrils ; 
hence  involuntary  mus- 
cles are  called  smooth 
Involuntary  Muscle  Cells 

(or fibers).  or    uustripcd   muscles. 


Fig.  41.  —  Two  Mus- 
cle Fibers  oe 
Heart. 


Fig.  42. 


THE  MUSCLES 


41 


The  heart  fibers  are  exceptional ;  they  are  the  only  invol- 
untary muscle  fibers  that  are  striped  (Fig.  41 ). 

Thought  Questions.  Classification  of  Some  of  the  Muscles.  — 
Copy  the  following  list  and  mark  /for  involuntary  and  V  for  voluntary 
after  the  appropriate  muscles. 

Muscles  for  chewing.       Muscles  of  gullet.      Muscles  of  the  heart. 
Muscles  that  move  arms.       Muscles  for  breathing.       Muscles  in  the  skin 
that  cause  the  hair  to  stand  on  end.        Muscles  that  move  eyelids. 
Muscles    that  contract  pupil  of  eye.       Muscles  for  talking.       Muscles 
that  contract  and  expand  the  arteries   (in  blushing  and  turning  pale). 
Muscles  that  move  eyeball.       Muscles  that  give  expression  to  the  face. 

Tendons.  —  The  connective  tissue  which  binds  1 'he  fibers  of 
muscles  into  bundles,  and  forms  sheaths  for  the  bundles, 
extends  beyond  the  ends  of  the  muscles  and  unites  to  form 
tough,  inelastic  white  cords  called  tendons.  Some  muscles 
are  without  tendons,  and  are  attached  directly  to  bones. 
Study  the  figures  and  find  examples  of  this  (see  Figs. 
44,  75).  To  realize  the  toughness  of  tendons,  feel  the 
tendons  under  the  bent  knee  or  elbow,  where  they  feel 
almost  as  hard  as  wires.  The  tendons  save  space  in  places 
where  there  is  not  room  enough 
for  the  muscles,  and  permit  the 
bulky  muscles  to  be  located  where 
they  are  out  of  the  way.  Wher- 
ever the  tendons  would  rise  out  of 
position  when  a  joint  is  bent,  as 
at  the  wrist  and  ankle,  they  are 
bound  down  by  a  ligament. 

Arrangement  of  Voluntary  Mus- 
cles. —  Circular  muscles,  called 
sphincter  muscles,  are  found  around 
the  mouth  and  eyes.  Muscles  that 
extend  straight  along  the  limb  either  bend  it  and  are  called 
flexors,  or  straighten  it  and  are  called  extensors.     Most  of 


Fig.  43.  —  (For  blackboard.) 
Biceps  relaxed  and  contracted. 


42  HUMAN  BIOLOGY 

the  voluntary  muscles  are  arranged  in  pairs  and  cause 
motion  in  opposite  directions  ;  they  are  said  to  be  antago- 
nists. The  biceps  (Fig.  43)  bends  the  arm.  Its  antagonist 
is  the  triceps  on  the  back  of  the  arm.  By  feeling  them 
swell  and  harden  as  they  shorten,  locate  on  your  own 
body  the  muscles  mentioned  in  Fig.  44. 

How  a  Muscle  grows  Stronger ;  its  Blood  Supply.  — 
Nature  has  provided  that  any  part  of  the  body  shall  receive 
more  blood  when  it  is  working  than  when  it  is  resting. 
When  it  works  the  hardest,  the  blood  tubes  expand  the  most 
and  its  blood  supply  is  greatest.  So  whenever  a  muscle  is 
used  a  great  deal,  an  unusual  amount  of  material  is  carried 
to  it  by  the  blood,  the  cells  enlarge  and  multiply,  and  the 
muscle  grows.  The  walls  of  the  capillaries  are  so  thin  that 
the  food  which  is  in  the  blood  readily  passes  from  them  to 
the  muscle.  Because  of  the  oxidation  taking  place,  a  work- 
ing muscle  is  warmer  than  one  at  rest.  By  use  a  muscle 
grows  large,  firm,  and  of  a  darker  red;  by  disuse,  it  be- 
comes small,  flabby,  and  pale.  But  if  muscles  are  worked 
too  constantly,  especially  in  youth,  their  cells  do  not  have 
time  to  assimilate  food  and  oxygen,  and  their  growth  is 
stunted. 

Unless  the  meal  has  been  a  very  light  one,  vigorous 
exercise  should  not  be  taken  after  eating,  as  the  blood  will 
be  drawn  from  the  food  tube  to  the  muscles  and  the  secre- 
tion of  the  digestive  fluids  will  be  hindered.  Persons 
whose  entire  circulation  is  weak  may  find  that  light  exercise 
after  a  meal,  such  as  walking  slowly,  may  help  circulation 
and  digestion. 

Why  the  Muscles  work  in  Harmony.  —  When  a  boy  throws 
a  stone,  almost  every  part  of  the  body  is  concerned  in  the 
action.  His  arms,  his  legs,  his  eyes,  the  breathing,  the 
beating  of  the  heart,  are  all  modified  to  assist  in  the  effort. 


Illustrated  Study  of  Muscular  Function 

Draw  a  dotted  line  from  each  function  mentioned  on  margin  to  the  muscle 
or  muscles  having  that  function. 


Bows  the  head? 


\       Draws  shoulder  back? 


arm  outward 


arm  downward 


elbow  ? 


Bends  the  fingers? 


Raises  the  body  on  the 


Raises  toes? 


Fig.  44.  — Superficial  Muscles  after  the  Statue  of  "The  Digger" 

(Lami) . 


43 


44 


HUMAN  BIOLOGY 


As  the  boy  wills  to  throw  the  stone,  nerve  impulses  are 
sent  to  all  the  organs  that  can  assist,  and  they  are  excited 
to  just  the  amount  of  action  needed. 

The  Nerve  Impulse  and  the  Contraction.  —  Each  nerve 
that  goes  to  a  muscle  is  composed  of  many  fibers;  the 
fibers  soon  separate  and  go  to  all  parts  of  the  muscle, 
and  each  muscle  fiber  receives  its  nerve  fiber  (see  Fig.  45). 

In  the  brain  each  fiber  is 
stimulated  at  once,  and  all 
the  fibers  shorten  and  thicken 
together.  This  change  is 
spoken  of  as  contraction  ;  but 
since  the  muscle  does  not  be- 
come smaller,  the  word  may 
be  misleading.  When  the 
muscle  shortens,  it  thickens 
in  proportion  and  occupies  as 
much  space  as  it  did  when 
relaxed. 

Where  does  Muscular  En- 
ergy come  from? — The  nerve 
does  not  furnish  the  energy 
which  the  muscle  uses  when 
contracting.  The  muscle  cells 
have  already  stored  up  energy  from  the  food  and  oxygen 
brought  to  them  by  the  blood,  and  the  process  called  oxida- 
tion sets  free  the  energy.  Activity  of  muscle  may  increase 
the  carbon  dioxid  output  fivefold.  Mental  work  has  prac- 
tically no  effect  upon  it. 

How  a  Muscle  stays  Contracted.  —The  muscle  relaxes  at 
once  after  contraction  ;  and  in  order  to  keep  it  contracted, 
nerve  impulses  must  be  sent  in  quick  succession,  causing 
in  fact  many  contractions ;  the  effect  of  this  is  sometimes 


Fig.  45.  —  Motor  Nerve  Fibers 
ending  among  fibrils  of  voluntary 
muscle.      Compare  with  Fig.  48. 


THE  MUSCLES 


45 


visible,  as  the  trembling  of  the  muscle.     Figure  47  shows 
an  easy  standing  posture. 

What  causes  Fatigue.  —  Fatigue  or  exhaustion  is  due  to 
the  using  up  of  the  living  material  in  the  nerve  cells  and 
muscle  cells  by  oxidation.  Rest  is  necessary  to  give  cells 
opportunity  to  repair  themselves.  Why  is  it  less  fatiguing 
to  walk  for  an  hour  than  to  stand  perfectly  still  for  ten 
minutes  ? 


Fig.  46.— Improper  Position; 
causes  spine  to  curve  to  side; 
raises  one  hip  and  shoulder 
above  the  other. 


Fig.  47.  —  Best  Position; 
chest  is  free  to  expand, 
and  weight  is  easily  shifted 
from  one  foot  to  other. 


Degeneration  of  Muscles  begins  with  habitual  disuse. 
We  dare  not  furnish  a  substitute  for  the  work  of  a  muscle, 
if  we  wish  the  muscle  to  remain  sound.  A  belt  or  a  stay 
at  the  waist  will  cause  the  muscles  of  the  trunk  to  become 
flabby  and  the  abdomen  to  relax  and  protrude. 

How  Muscular  Activity  helps  the  Health.  —  Life  is 
change,  stagnation  is  death.    Muscular  activity  uses  up  the 


46 


HUMAN  BIOLOGY 


food,  gives  a  good  appetite,  and  sets  the  digestive  organs  to 
work;  it  uses  np  the  oxygen  and  sets  the  lungs  to  work; 
but  most  of  all,  every  contraction  of  a  muscle  helps  the  blood 
to  flow.  As  a  muscle  contracts,  it  presses  upon  the  veins 
and    lymphatics,  and,  by  this   pressure,  forces   the   blood 

and  lymph  along  (Fig. 
48).  In  any  ordinary 
activity,  dozens  of  mus- 
cles are  being  used. 
That  the  effect  upon  the 
circulation  is  very  pow- 
erful, is  shown  by  the 
rosy  skin,  deep  breath- 
ing, and  rapid  heart  beat. 
The  many  benefits  of  an 
active  circulation  of  the 
blood  and  lymph  will 
be  discussed  in  the  next 
chapter.  See  page  67. 
A  grave  danger  from  athletics  is  that  of  developing  the 
muscles,  including  the  heart,  to  an  enormous  extent  by 
training ;  then  when  training  ceases  the  muscles  undergo 
fatty  degeneration  from  disuse.  Heart  disease  and  other 
diseases  may  follow.  Many  athletes  die  young,  killed  by 
trying  to  turn  their  bodies  into  mere  machines  for  run- 
ning, boxing,  or  rowing,  instead  of  living  complete  lives. 
The  athletic  ideal  is  not  the  highest  ideal  of  health ;  gen- 
eral activity,  resembling  the  occupations  of  hunting  and 
farming  by  which  the  early  race  supported  itself,  is 
best  for  health.  Many  kinds  of  factory  work  use  only 
one  set  of  muscles.  The  savage  did  not  lead  a  monoto- 
nous life,  and  monotony  is  bad  for  both  muscles  and 
nerves. 


Fig.  48.  —  Capillaries  among  fibers  of 
voluntary  (cross  striped)  muscle.    (Peabody.) 


THE  MUSCLES 


47 


Advantages  of  Work  and 
Play  over  Gymnastic  Exer- 
cises. —  The  interest  that 
comes  from  doing  something 
useful,  makes  muscular  exer- 
tion doubly  beneficial  to  the 
health.  The  lifting  of  dumb- 
bells, Indian  clubs,  and  pulley 
weights,  and  letting  them 
down  again,  tends  to  become 
very  irksome,  even  though 
done  with  the  knowledge  that 
the  exercise  will  benefit  the 
health.  Useful  labor  and 
games  place  defijiite  objects  in 
view  and  do  not  require  so 
great  an  effort  of  the  will  nor 
exhaust  the  nerves  so  much  as 
mere  exercise.  The  interest 
in  the  work  or  the  game  serves 
to  arouse  all  the  nerves  and 
muscles  to  work  in  harmony. 

An  Advantage  of  Gymnas- 
tics over  Work  and  Play.  — 
Gymnastics  can  furnish  any 
required  variety  of  exercises 
and  can  develop  exactly  the 
muscles  that  need  develop- 
ment and  leave  those  idle  that 
have  become  overdeveloped  by 
doing  constantly  one  kind  of 
work  or  playing  continually 
the  same  game.  The  deform- 
ity of  a  flat  chest  (and  round 
shoulders  which  always  ac- 
company it)  does  not  so  often 
indicate  a  weak  chest  or  small 
lungs  as  it  indicates  weak  or 
relaxed  muscles  of  the  back 
and  the  habit  of  sitting  in  a 
relaxed  position  at  work 
(Figs.  49,  50,  51).     Gymnas- 


Di 


Ogi-) 


Fig.  50. —  Correct  Position. 


Fig.  51.  —  Slipping  down  in  Seat. 


48  HUMAN  BIOLOGY 

tic  exercise  is  not  wholly  an  artificial  custom.  Cats  stretch  themselves, 
stretching  each  leg  in  succession  ;  many  animals  gambol  and  play.  A 
gymnastic  drill,  taken  to  music  and  with  large  numbers  of  pupils  in 
the  drill,  is  interesting  as  work  or  play,  and  should  not  be  neglected  for 
any  study,  however  important. 

Environment  of  Early  Man  and  Modern  Man.  —  A  well-developed 
man  of  one  hundred  and  fifty  pounds  weight  should  have  sixty  pounds 
of  muscles.  The  proportion  is  often  different  in  the  puny  bodies  of  the 
average  civilized  men,  such  as  clerks,  merchants,  lawyers,  and  other 
men  with  sedentary  occupations  ;  their  bodies  are  as  likely  to  be  lean 
and  scrawny  or  fat  and  flabby  as  to  be  correctly  proportioned.  Why 
does  a  jiormal  man  have  sixty  pounds  of  muscles  instead  of  twenty 
pounds  of  puny  strings  such  as  would  have  sufficed  for  a  clerk,  student, 
or  a  writer?  This  is  because,  in  his  native  condition,  he  had  to  seek 
his  food  by  roaming  through  the  forest,  contending  with  wild  beasts 
or  with  other  savage  men,  often  traveling  many  miles  a  day,  climbing 
trees,  etc. 

Too  Rapid  Change  of  Environment ;  Destructive  Tendencies  of  Civil- 
ization. —  //  is  impossible  for  the  human  body  to  change  greatly  in  a  few 
hundred  years.  The  body  of  man  served  him  for  many  ages  for  the 
manner  of  life  outlined  above.  It  was  suited  for  these  conditions,  and 
the  muscles  and  the  organs  that  support  them  cannot  accommodate 
themselves  to  changed  conditions  in  a  few  generations.  It  has  only 
been  a  few  hundred  years  since  the  ancestors  of  the  Britons  and  Ger- 
mans, for  instance,  were  running  wild  in  the  German  forests,  clad  in  the 
skins  of  wild  beasts.  Yet  civilized  man  lets  his  muscles  fall  info  disuse, 
he  takes  a  trolley  car  or  horse  vehicle  to  go  half  a  mile,  an  elevator  to 
climb  to  the  height  of  thirty  feet.  He  neglects  all  his  muscles  except 
those  that  move  the  tongue  and  the  fingers  of  the  right  hand.  He 
never  makes  enough  exertion  to  cause  him  to  draw  a  deep  breath,  and 
his  lungs  contract  and  shrivel.  He  seldom  looks  at  anything  farther 
than  a  few  inches  from  his  nose,  and  his  eyes  become  weak.  At  the 
same  time  that  he  neglects  his  muscles  and  his  lungs,  he  overworks  his 
brain  and  his  stomach  ;  yet  he  expects  his  body  to  undergo  the  rapid 
changes  to  suit  the  demands  of  his  life.  Such  rapid  changes  in  the 
human  race  are  impossible.  A  man  that  does  not  see  that  sound  health 
is  the' most  valuable  thing  in  the  world,  except  a  clear  conscience,  is  in 
danger  both  of  wrecking  his  own  happiness  and  of  failing  in  his  duty 
to  others. 

Thought  Questions.  Shoes. — 1.  What  the  faults  of  shoes  may 
be  in  size  ;  shape  ;  sole  ;  heel ;  toe  ;  instep.  2.  Name  deformities  re- 
sulting to  skin  of  foot ;  nails  ;  joints  ;  arch  ;  ankle  ;  spine.    3.  State  effects 


THE  MUSCLES  49 

of  uncomfortable  shoes  on  muscular  activity;  mind  and  disposition. 
4.  State  effect  of  aversion  to  walking  on  muscles  ;  circulation.  5.  If 
a  shoe  is  too  loose,  it  slips  up  and  down  at  the  heel  and  chafes  the  skin 
there ;  if  too  tight,  there  is  pres- 
sure on  the  toes,  which  causes  a 
corn  or  ingrowing  nail.  Have 
your  shoes  been  correct,  or  have 
they  been  too  loose  or  too  tight? 

According  to  this  test,  what  pro-     _, 

jr         .  ,  ,         Fig.  52. —  Arch  of  Foot.    It  forms  an 

portion  of  people  wear  shoes  that  e]astlc  spring_ 

are   too  tight?     6.    How   many 

sprained  ankles  have  you  known  among   boys;    girls?     7.  Why  is  it 

that  people  who  grow  up  in  warm  climates  have  high,  arched  insteps, 

and  short,  broad,  elastic  feet,  but  people  of  the  same  race  who  pass  their 

childhood  in  cold  climates  often  have  long  narrow  feet  with  low  arches 

and  sometimes  have  the  deformity  called  "  flat  foot  "  ? 

Instinct  as  a  Guide  for  using  the  Muscles.  —  The  instinctive  feeling 
called  fatigue  tells  us  when  to  rest.  There  is  also  a  restless,  uneasy 
feeling  that  comes  over  a  normal  human  being  when  confinement  and 
restraint  of  the  muscles  have  reached  an  unhealthy  limit.  This  feeling 
should  not  be  repressed  for  long  at  a  time.  Many,  ruled  bv  avarice, 
ambition,  interest  in  sedentary  work,  a  silly  notion  of  respectability,  or 
a  false  conception  of  duty,  have  repressed  this  feeling  and  have  lost 
it.  There  is  then  a  feeling  of  languor,  and  a  disinclination  to  the  very 
activity  which  health  demands.  An  unheeded  instinct  is  as  useless  as 
an  alarm  clock  that  has  been  habitually  disregarded. 

Exercise  and  Climate.  —  In  our  warmest  states  and  in  the  tropics, 
one  hour's  vigorous  physical  labor  a  day,  combined  with  the  ordinary 
activities  of  life,  will  keep  a  person  in  good  condition.  In  the  colder 
states,  muscular  exertion  for  several  hours  is  needed  daily. 

Complete  Living.  —  Numberless  people  have  devoted  themselves  to 
an  intellectual  occupation,  and  planned  to  keep  their  bodies  sound  by 
gymnastics  and  special  exercises.  Because  of  the  monotony  of  exer- 
cises, they  are  soon  given  up  in  nearly  every  instance.  The  safest  way 
is  never  to  allow  all  the  energies  to  be  devoted  to  a  one-sided  occupation, 
but  so  to  plan  one^s  life  and  work  that  a  part  of  the  time  is  devoted  to 
some  physical  work,  whether  it  be  in  a  garden,  workshop,  or  orchard  ; 
in  walking  a  long  distance  to  the  office;  at  bookbinding,  cooking,  wood 
carving,  or  any  one  of  various  other  useful  occupations.  The  result  of 
manual  training  shows  that  not  only  strength  of  body,  but  strength  of 
mind,  is  promoted  by  physical  labor.  Problems  of  war  and  of  the  chase 
kept  active  both  the  body  and  mind  of  the  savage.      Hence  he   led 

E 


50  HUMAN  BIOLOGY 

a  more  nearly  complete  life  than  his  civilized  descendants,  and  his  body 
was  strong  accordingly.  We  should  admit  the  hopelessness  of  having 
permanent  good  health  without  muscular  activity  and  should  determine 
that  muscular  exertion  shall  be  as  much  a  habit  and  pleasure  as  eating 
and  sleeping. 

Alcohol  and  Muscular  Strength. —  Benjamin  Franklin,  one  of  the 
wisest  and  greatest  of  Americans,  was  a  printer  when  he  was  a  young 
man.  In  his  autobiography  he  gives  an  account  of  his  experience  as  a 
printer  in  London.  He  says:  "I  drank  only  water;  the  other  work- 
men, fifteen  in  number,  were  great  drinkers  of  beer.  On  occasion  I 
carried  up  and  clown  stairs  a  large  form  of  types  in  each  hand,  when 
others  carried  but  one  in  both  hands.  They  wondered  to  see,  from  this 
and  several  instances,  that  the  Water-American,  as  they  called  me,  was 
stronger  than  themselves,  who  drank  strong  beer.  My  companion  at 
the  press  drank  every  day  a  pint  before  breakfast,  a  pint  at  breakfast 
with  his  bread  and  cheese,  a  pint  between  breakfast  and  dinner,  a  pint  at 
dinner,  a  pint  in  the  afternoon  about  6  o'clock,  and  another  when  he  had 
done  his  day's  work.  I  thought  it  a  detestable  custom,  but  it  was  neces- 
sarv.  he  supposed,  to  drink  strong  beer  that  he  might  be  strong  to  labor." 

Exercises  in  Writing.  — The  Right  and  the  Wrong  Way  to  ride 
a  Bicycle.  Pay  Day  at  a  Factory.  A  Graceful  Form  :  how  Acquired  ; 
how  Lost.     A  Drinking  Engineer  and  a  Railway  Wreck. 

Practical  Questions!  —  1.  Can  we  always  control  the  voluntary 
^.muscles?  Do  we  shiver  with  the  voluntary  or  involuntary  muscles? 
2.  If  a  man  had  absolute  control  over  his  muscles  of  respiration, 
what  might  he  do  that  he  cannot  now  do?  3.  Why  is  one  who  uses 
alcoholic  drinks  not  likely  to  be  a  good  marksman?  4.  Why  should  a 
youth  who  wishes  to  excel  in  athletic  contests  abstain  from  the  use 
of  tobacco?  5.  Is  there  any  relation  between  the  amount  of  bodily 
exertion  necessary  for  a  person's  health  and  the  amount  of  wealth  or 
the  amount  of  intelligence  he  possesses?  6.  Can  you  relax  the  chewing 
muscles  so  that  the  lower  jaw  will  swing  loosely  when  the  head  is 
shaken?  Can  you  relax  your  arm  so  that  it  falls  like  a  rope  if  another 
person  raises  it  and  lets  it  fall?  7.  The  average  man  has  sixty  pounds 
of  muscle  and  two  pounds  of  brain  ;  one  half  of  the  blood  goes  through 
the  muscles  and  less  than  one  fifth  goes  through  the  brain.  What 
inference  may  you  draw  as  to  the  kind  of  life  we  should  lead?  8.  Why 
>4s  a  slow  walk  of  little  value  as  exercise?  9.  How  can  we  best  prove 
that  we  have  admiration  and  respect  for  our  wonderful  bodies? 
10.  Why  is  the  ability  to  relax  the  muscles  thoroughly  of  great  benefit 
to  the  health?  How  is  this  ability  tested?  (Question 6.)  11.  Why  is 
it  as  correct  to  say  that  the  muscles  support  the  skeleton  as  the  reverse? 


^V     „F  THE 

UNIVERSITY 

OF 
rAL'FO?*£> 


Head   arteries 

•  lid). 

Nameless  art*  ries 
innominate). 

ione  (sub- 
■  lavi  in 

ndofthe 
aorta. 


18.    Ascending    vena 
cava. 
Vein    from    liver 
(hepati 

ao.    Vein  from  stom- 
ach (gastrii 

11.    Vein     from 
spleen. 


5.    Pulmonary 
arteries. 
6    Thoracic  aorta. 

7.  10.    Abdominal 

aorta 

8.  Artery  to  liver 

(hepatic). 

9.  Artery  to  spleen 

(splenic  . 

11.  Artery  to  in- 

testine 
(mesenteric).  .- 

12.  Artery  to  1 

kidney 
(renal). 

13.  Descending       f 

vena  cava.      • 

14.  Nameless  vein  - 

(innominate, 
15  and  16  be- 
fore branching) 

15.  Collar  bone  vein 

(subclavian). 
16     Jugular  vein. 
17.    Pulmonary  vein. 


Vein  from 

intestine. 
Vein  to  liver 

(portal). 
Vein  from 

kidney. 
Right  auricle. 
Left  auricle 

27.  Righ*.  ven- 
tricle. 

28.  Left  ventri- 
cle. 

Thoracic 
duct. 
jo.    Stomach. 

31.  Spleen. 

32.  Liver. 
Kidneys. 
Duodenum. 

,    Ascending  colon. 
Descending 
colon. 
yinphatic  glands 
of  mesentery. 


Colored  Figure  5.    Diagram  of  Circulation. 


CHAPTER   V 
THE   CIRCULATION 

Experiment  i .  Anatomy  of  Mammalian  Heart.  —  Get  a  sheep's 
or  beef's  heart  from  the  butcher.  Get  the  whole  heart,  not  simply  the 
ventricles  (as  usually  sold).  Note  the  blood  vessels,  four  chambers, 
thickness  of  different  walls,  valves,  cords,  openings. 

Experiment  2.  Does  Gravity  affect  the  Blood  Flow?  —  Hold  the 
right  hand  above  the  head  for  a  few  minutes.  At  the  same  time  let  the 
left  hand  hang  straight  down.  Then  bring  the  hands  together  and  see 
which  is  of  a  darker  red  because  of  containing  more  blood.  Now  re- 
verse the  position  of  the  hands  for  a  few  minutes,  and  find  whether  the 
effect  is  reversed.     (Entire  class.) 

Experiment  3.  Study  of  Human  Blood.  —  Examine  a  drop  of  blood 
under  the  microscope,  first  diluting  it  with  a  little  saliva.     See  Fig  60. 

Experiment  4.  The  Circulation  in  a  Frog.  —  Wrap  a  small  frog  in  a 
moist  cloth,  lay  on  a  slip  of  glass,  place  under  the  microscope,  and 
study  the  circulation  in  the  web  of  its  foot. 

Experiment  5.  (Entire  class.)  Effect  of  Exercise  upon  the  Pulse. — 
Tap  a  bell  as  the  second  hand  of  a  watch  begins  a  minute  and  let  the 
pupils  count  the  pulse  at  the  radial  artery  on  the  wrist  above  base  of 
thumb.     Repeat  standing,  or  after  gymnastics  or  recess.     Result? 

Experiment  6.  The  Action  of  the  Valves  in  the  Veins.  —  Place  the 
tip  of  the  middle  finger  on  one  of  the  large  veins  of  the  wrist :  with 
the  forefinger  then  stroke  the  vein  toward  the  elbow  so  as  to  push  the 
blood  from  a  portion  of  it,  keeping  both  fingers  in  place.  The  vein 
remains  empty  between  the  fingers.  Lift  the  finger  nearer  the  heart 
and  no  blood  enters  the  vein  ;  there  is  a  vali'e  ab<n>e  which  holds  it  back. 
Lift  the  other  finger  and  the  vein  fills  instantly.  Stroke  a  vein  toward 
the  hand,  and  notice  that  the  the  veins  swell  up  into  little  knots  where 
the  valves  are.      Stroke  in  the  reverse  direction.     Result  ? 

Experiment  7.  Finding  the  Capillary  Pressure.  This  is  found  by 
pressing  a  glass  plate  or  tumbler  upon  a  red  part  of  the  skin.  When 
the  skin  becomes  pale  the  capillary  pressure  is  counterbalanced. 

Experiment  8.  Emergency  Drill.  —  Let  one  pupil  come  forward,  mark 
with  blue  chalk  or  pencil  the  position  on  his  arm  of  a  supposedlv  cut 
vein.     Let  another  pupil  use  means  to  stop  the  imagined  blood  flow. 

5i 


52 


HUMAN  BIOLOGY 


Experiment  9.  Let  another  pupil  stop  the  flow  from  an  imaginary  cut 
artery  marked  red.  See  text.  Experiment  10.  In  a  case  of  nose  bleed 
do  not  let  pupil  lean  over  a  bowl.  (Why?)  Cause  him  to  stand 
rather  than  lie.  (Why?  See  Exp.  2.)  Apply  cold  water  to  contract 
arteries  to  nose,  also  have  pupil  hold  a  small  roll  of  paper  or  a  coin 
under  upper  lip  (to  make  muscular  pressure  on  arteries  to  nose). 
Experiment  11.  Let  one  pupil  treat  another  for  a  bruise  (see  p.  62). 
Experiment  12.     Emergency  drill,  restoration  from  fainting  (see  p.  57). 

The  Cells  have  a  Liquid  Home.  —  The  cells  in  the  body  of  man,  like 
the  ameba,  live  in  a  watery  liquid.  This  liquid  is  called  lymph.  The 
cells  cannot  move  about  as  the  ameba  does  to  obtain  food,  so  the 
blood  brings  the  food  near  them  and  it  soaks  through  the  blood  tubes 
into  the  lymph  spaces  next  to  the  cells  (see  colored  Fig.  3).  The 
ameba  gives  off  waste  material  into  the  water;  the  cells  of  the  body 
give  it  off  into  the  lymph  to  be  carried  off  by  the  circulation.  The 
blood,  then,  has  two  functions :  (1)  to  take  nourishment  to  the  tissues; 
(2)  to  take  away  waste  material  from  them. 

The  Organs  of  Circulation.  —  These  are  the  heart,  which 
propels  the  blood ;  the  arteries,  which  take  blood  away 
from  the  heart ;  the  reins,  which  take 
the  blood  back  to  the  heart ;  and  the 
capillaries  (Fig.  53),  which  take  the 
blood  from  the  arteries  to  the  veins. 

The  heart  is  a  cone-shaped  organ 
about  the  size  of  its  owner's  fist.  It 
lies  in  a  diagonal  position  behind  the 
breastbone,  with  the  small  end  of  the 
cone  extending  toward  the  left.  The 
smaller  end  (Exp.  1)  taps  or  beats 
against  the  chest  wall  at  a  point  be- 
tween the  fifth  and  sixth  ribs  on  the  left  side.  The 
breastbone  and  ribs  protect  it  from  blows.  An  inclosing 
membrane  called  the  pericardium  secretes  a  serous  fluid 
and  lessens  the  friction  from  its  beating. 

Why  the  Heart  is  Double.  —  There  must  be  a  pump  to  move 
the  impure  blood  from  the  body  to  the  lungs  to  get  oxygen 


Fig.  53.  —  Capillaries, 
connecting  artery  [b) 
with  vein  (a). 


THE    CIRCULATW.X 


53 


from  the  air,  and  there  must  be  another  pump  to  send  the 
pure  blood  front  the  limgs  back  to  the  body.  Hence  there 
are  two  pumps  bound  together  into  one  heart,  beating  at 
the  same  time  like  two  men  keeping  step,  or  like  two  car- 
penters keeping  time  with  their  hammers.  There  are 
valves  in  the  heart,  as  in  other  pumps.  These  valves  are 
so  arranged  that  when  any  part  of  the  heart  contracts  and 
forces  the  blood  onward,  the  blood  cannot  return  after  that 
part  of  the  heart  relaxes.  Are  the  pumps  placed  one 
behind  the  other?  Or  is  one  above  the  other?  Neither; 
they  are  side  by  side,  with  a 
fleshy  partition  between  them 
(Fig.  54).  The  pump  on  the  £ 
right  moves  the  impure  blood  $ 
from    the    body    to    the 

.  ,     .  ,  purmonary 

lungs,  and  the  one  on  the        veins 
left  moves  the  pure  blood 
from   the  lungs  to   the .  body. 
There  is  no  direct  connection 
between  the  right  and  left  sides 
of  the  heart. 

To  trace  one  complete  circuit 
of  the  blood  (Fig.  54),  let  us 
begin  with  the  blood  in  the 
capillaries  of  the  outer  tissues, 
such  as  the  skin  or  muscles. 
The  blood  goes  through  small 
veins  which  unite  into  tzvo 
large  veins,  through  which  it 
enters  the  receiving  chamber,  or  right  auricle,  goes  through 
the  tricuspid  valve  into  the  expelling  chamber,  or  right 
ventricle,  then  through  a  semilunar  valve  into  the  pulmo- 
nary artery  leading  to  the  lungs.     Becoming  purified  while 


Fig.  54.  —  Diagram  of  Heart. 

Notice  the  two  dark  spots  in  the  right 
auricle,  and  four  dark  spots  in  left 
auricle,  where  the  veins  enter.  Does 
the  aorta  pass  in  front  of,  or  behind, 
the  pulmonary  artery? 


54 


HUMAN  BIOLOGY 


passing  through  the  capillaries  of  tlic  lungs,  the  blood  goes 
through  the  pulmonary  veins  to  the  left  auricle  (Fig.  54), 
then  through  the  bicuspid  or  mitral  valve,  to  the  left  ventri- 
cle, whence  it  is  forced  through  a  semilunar  valve  into  the 
largest  artery  of  the  body,  called  the  great  aorta  (Fig.  54). 
Thence  it  goes  to  the  smaller  arteries,  and  then  to  the  capil- 
laries of  the  tissues  in  general,  thus  completing  the  circuit. 


Fig.  55.  —  The  Lkft  Side  of  Heart  (plan),  showing  the  left  ventricle  at  the  mo- 
ment when  relaxing  and  receiving  the  blood  from  the  auricle;  and  the  same  at 
the  beginning  of  contraction  to  send  blood  into  aorta.    Notice  action  of  the  valve. 

Structure  of  Veins  and  Arteries.  —  Seen  under  the  micro- 
scope the  arteries  and  veins  show  that  they  are  made  of 
t lire e  kinds  of  tissues  arranged  in  three  coats  (Fig.  56):  a 
tissue  resembling  epithelial  tissue  (Chap.  I),  as  a  lining 
to  lessen  friction  ;  an  outer  connective  tissue  (Chap.  I),  to 
give  elasticity ;  and  a  middle  coat  of  muscular  tissue  to 
enable  the  vessels  to  change  in  size.  Let  us  see  why  blood 
vessels  must  have  these  three  properties? 

Why  the  Blood  Vessels  must  be  Elastic.  — The  aorta  and  its  branches 
are  always  full  of  blood.  When  the  left  ventricle  with  its  strong,  mus- 
cular walls  contracts,  the  blood  in  the  aorta  and  small  blood  tubes  can- 
not move  forward  fast  enough  to  make  room  for  the  new  supply  so 
suddenly  scut  out  of  the  ventricle.     Where  can  this  blood  go  ?     If  a 


THE    CIRCULATION 


55 


In  men 


cup  is  full,  it  cannot  become  more  full;  not  so  with  an  artery.  The 
elastic  connective  tissue  allows  it  to  expand  as  a  rubber  hose  does 
under  pressure.  The  first  part  of  the  aorta  having  expanded  to  receive 
the  incoming  blood,  the  stretched  walls  contract  because  of  the  elas- 
ticity of  the  outer  connective  tissue  coat  and  force  blood  into  the  por- 
tion of  the  aorta  just  ahead,  forcing  it  to  expand  in  turn.  Thus  a  wave 
of  expansion  travels  along  the  arteries.     This  wave  is  called  the  pulse. 

The  Pulse  may  be  most  easily  felt  in  the  wrists  and  neck.  As  the 
artery  stretches  and  springs  back,  one  beat  of  the  pulse  is  felt 
there  are  about  seventy  heart  beats  or 
pulse  beats  a  minute.  In  women  the 
rate  is  about  eighty  a  minute.  It  is 
slowest  when  one  is  lying  down,  faster 
while  sitting,  still  faster  when  stand- 
ing, and  fastest  of  all  during  running  or 
violent  exercise.  (Exp.  5.)  It  should 
not  be  thought  that  the  muscular  or 
middle  layer  of  the  artery  actively  con- 
tracts and  helps  to  send  along  the  pulse 
wave  ;  for  this  wave  is  simply  the  pas- 
sive stretching  and  contracting  of  the 
outer  connective  coat,  and  travels  like 
a  wave  crossing  a  pond  when  a  stone 
is  dropped  into  the  water.  The  force 
of  the  pulse  is  furnished,  not  by  the 
muscle  fibers  in  the  artery,  but  by  the 
beat  of  the  heart ;  the  outer,  or  con- 
nective tissue,  coat  enables  the  pulse 
to  travel.  Why  must  there  be  a  mid- 
dle, or  muscular,  coat  for  variation  in 
size? 

Use  of  the  Middle  Coat :  Quantity  of 
Blood  and  its  Distribution.  —  The  body 
of  an  adult  contains  about  five  quarts 
of  blood.  The  blood  furnishes  the  nourishment  needed  for  the  activity 
of  each  organ.  The  more  vigorous  the  work  of  any  organ,  the  greater 
is  the  amount  of  blood  needed.  The  whole  amount  of  blood  in  the  body 
cannot  be  suddenly  increased,  but  the  muscular  coat  of  the  arteries  going 
to  the  working  organ  relaxes,  and  allows  the  arteries  to  become  enlarged 
by  the  pressure  from  the  heart.  Consequently,  more  blood  goes  to  the 
active  organ,  and  the  other  organs  get  along  with  less  blood  for  the  time. 
When  we  are  studying,  our  brains  get  more  blood ;  when  running,  the 


Fig.  56. —  Section  of  Artery, 
A,  AND  Vein,  V,  showing  inner 
coat,  e  (endothelial)  ;  middle 
coat,  m  (muscular)  ;  and  third 
coat,  a  (connective  tissue). 


56 


HUMAN  BIOLOGY 


Fig.  57.  —  Capillaries  Magni- 
fied, showing  Cells  forming 
their  walls.  Notice  that  each  cell 
has  a  nucleus  and  three  branches. 


leg  muscles  get  more ;  after  a  hearty  dinner,  the  stomach  and  intestines 
get  more  than  any  other  part  of  the  body.     Why  is  it  difficult  to  do  the 

best  studying  and  digest  a  meal  at  the 
same  time?  We  see  that  the  muscu- 
lar coat  of  the  arteries  is  a  very  useful 
coat,  for  it  enables  the  supply  of  blood 
to  be  increased  in  any  organ  which  is 
in  temporary  need  of  it. 

Why  the  Blood  Vessels  must  be 
Smooth.  —  The  inner  coat  of  the  heart 
and  other  blood  vessels  is  made  of 
tissue  like  the  epithelial  tissue  which 
forms  the  epidermis  and  the  smooth 
lining  of  the  mouth  and  other  organs. 
The  purpose  of  this  lining  is  to  lessen 
friction,  and  thus  save  the  work  of 
the  heart.  The  friction  is  greatest  in 
the  capillaries  because  of  their  small 
size.  The  inner  coat  of  smooth  cells 
is  the  only  coat  that  is  prolonged  to 
form  the  capillaries  (see  Fig.  57). 

The  capillaries  are  small,  thin,  short,  and  very  numerous. 
They  arc  very  small  so  that  they  may  go  in  between  the 
cells  of  the  tissues.  The  capillaries  are  very  thin  so  that 
the  nourishment  from  the  blood  may  pass  readily  into  the 
tissues,  and  the  waste  material  pass  readily  into  the  blood. 
They  are  very  short  so  that  the  friction  may  be  less ;  and 
they  are  very  numerous  so  that  all  parts  of  the  tissues  may 
be  supplied  with  blood,  and  that  the  blood  may  flow  very 
slowly  through  them.  Because  of  the  number  of  the  cap- 
illaries, their  total  volume  is  several  hundred  times  larger 
than  the  volume  of  the  arteries  that  empty  into  them,  or 
of  the  veins  that  flow  from  them.  Hence  the  blood 
flows  slowly  through  the  capillaries,  as  water  flows  slowly 
through  a  lake  along  the  course  of  a  river.  All  the 
changes  between  the  blood  and  the  lungs,  and  between 
the  blood  and  the  tissues,  take  place  in  the  capillaries,  and 


THE    CIRCULATION 


57 


the  object  of  the  other  parts  of  the  circulation  is  merely 
to  move  the  blood  continually  through  the  capillaries. 

The  effect  of  gravity  is  to  retard  the  flow  in  certain  parts  of  the 
body  and  aid  the  flow  in  other  parts,  according  to  the  position  of  the 
body  (Exp.  2). 

Fainting  is  usually  due  to  lack  of  blood  in  the  draw,  which  in  turn  results 
from  a  weakening  of  the  heart  beat.  Since  the  brain  cannot  work  with- 
out fresh  blood,  fainting  is  accompanied  by  unconsciousness.  Recov- 
ery from  fainting  is  aided  by  loosening  the  clothing  at  the  neck  and  by 
placing  the  head  of  the  patient  a  little  lower  than  the  body  so  that  the 
weight  of  the  blood  may  aid  the  flow  to  the  brain.  Dashing  a  little 
cold  water  in  the  face  shocks  the  nerves  and  arouses  the  heart  to 
stronger  beats. 

The  veins  have  valves  placed  frequently  along  their 
course  (Fig.  58).  These  valves  are  pockets  made  by  a 
fold  in  the  inner  coat  of  the  wall 
of  the  vein.  When  a  boy  places 
his  hand  in  his  pocket,  the  pocket 
swells  out ;  but  if  he  rubs  his  hand 
on  the  outside  of  the  pocket  from 
the  bottom  toward  the  top,  it  flat- 
tens down.  So  with  the  action  of 
the  blood  upon  the  valves  in  the 
veins.     (Repeat  Exp.  6  in  class.) 


I 

1 


Fig.  58.  — Valves  in  Veins. 
(Jeg>.) 


How  Muscular  Exercise  aids  the  Heart. 
—  When  a  muscle  contracts,  it  hardens  and 
presses  upon  a  vein  which  goes  through 
the  muscle,  and  the  blood  is  pressed  out  of  the  vein  (see  Fig.  58).  The 
blood  cannot  go  toward  the  capillaries,  for  the  valves  fill  and  close  when 
it  starts  that  way  ;  so  it  must  all  go  out  toward  the  heart.  When  the 
muscle  relaxes,  the  blood  that  has  been  pressed  forward  cannot  go  back 
because  of  the  valves,  but  the  valves  nearer  the  capillaries  open,  and  the 
veins  are  filed  from  the  capillaries  (Fig.  53).  When  the  muscle  con- 
tracts again,  the  same  effect  on  the  blood  movement  is  repeated.  We  see,  > 
therefore,  that  every  contracting  muscle  converts  into  a  pump  the  vein 
running  through  it,  and  when  a  person  works  or  exercises,  many  little 
pumps  are  working  all  over  the  body,  aiding  the  heart  in  its  function. 


58 


11  UMAX  1U0L0GY 


This  aid  makes  the  blood  flow  faster  and  relieves  the  heart  of  part  of 
its  work,  so  th.it  it  beats  faster,  just  as  a  horse  might  trot  faster  if 
another  horse  helped  to  draw  the  ioad  (Exp.  3).  The  pressure  of  a 
contracting  muscle  upon  an  artery  does  not  aid  the  blood  flow  in  the 
artery  because  the  latter  is  destitute  of  valves. 

How  Breathing  aids  the  Heart.  —  Breathing  is  a  blood-pumping  pro- 
cess as  well  as  an  air-renewing  process.  When  the  chest  expands, 
blood  is  drawn  into  it.  When  the  chest  con- 
tracts, the  flow  of  blood  away  from  it  is  aided. 
As  the  chest  expands,  the  downward  pressure 
of  a  great,  broad  muscle,  the  diaphragm  (Fig. 
74;  compresses  the  liver,  stomach,  and  other  ab- 
dominal organs,  and  forces  the  venous  biood  up- 
ward into  the  expanding  chest,  thus  helping  it 
on  its  way  to  the  heart.  But  if  the  abdominal 
wall  is  weakened  by  tight  lacing  or  by  the  pres- 
sure of  belts  and  bands  which  support  the  cloth- 
ing, the  weak  abdominal  wall  yields  to  the 
downward  pressure  of  the  diaphragm,  and  no 
compression  of  the  liver  or  aid  to  the  circulation 
will  result. 

How  the  Blood  Vessels  are  Controlled.  — Evi- 
dently the  biood  vessels  are  not  regulated  by  the 
will.  We  cannot  voluntarily  increase  the  beat- 
ing of  the  heart,  or  cause  it  to  slacken  its  action.  Even  an  actor  cannot 
cause  his  face  to  turn  pale  or  to  blush  at  will.  This  is  because  the 
tiny  muscles  in  the  walls  of  the  blood  vessels  are  involuntary  muscles. 
They  are  controlled  by  nerves  of  the  sympathetic  system  called  vaso- 
motors. They  are  not  subject  to  the  wil.'  (see  Fig.  25).  The  nerve  cen- 
ter which  controls  the  biood  vessels  is  located  in  the  top  of  the  spinal 
cord  at  the  base  of  the  brain.  When  cold  air  strikes  the  skin  the 
nerves  near  the  arteries  are  stimulated,  the  arteries  in  the  skin  contract, 
and  the  skin  turns  white.  When  the  heat  from  a  hot  fire  strikes  the 
skin,  the  nerves  are  soothed,  the  arteries  relax,  and  the  face  becomes 
red.  When  the  stomach  is  filled  with  food,  the  heart  beats  faster 
and  sends  more  blood  to  aid  in  digestion.  When  we  run  fast,  the 
heart  beats  fast  to  supply  more  blood  to  the  muscles,  but  it  slows  down 
as  sleep  comes  on,  that  the  body  and  brain  may  rest. 

Parts  of  the  Blood.  —  The  blood  which  flows  from  a  cut 
finger  seems  to  be  a  bright  red  throughout.  When  a  drop 
of  it    is  looked  at  through  a  microscope,    however,   the 


Fig.  59.  —The  Ven- 
tricles of  A 
Dog's   Heart 

relaxed  (above), 
and  contracted  (be- 
low). 


THE    CIRCULATION 


59 


liquid  itself  is  seen  to  be  almost  as  clear  as  water.  This 
liquid  is  called  the  plasma.  Floating  in  it  are  millions  of 
biconcave  disks  contain- 
ing a  pigment  (hemo- 
globin) which  gives  the 
red  color  to  the  blood. 
The  disks  are  called  red 
corpuscles  (Fig.  60).  A 
few  irregularly  shaped 
bodies,  nucleated  and 
almost  transparent,  and 
called  white  corpuscles, 
are  also  found  in  the 
blood.  The  red  corpus- 
cles go  only  where  the 
plasma  carries  them 
(Exps.  3,  4).  The  white 
corpuscles  sometimes  leave  the  blood  vessels  entirely. 
At  times  one  may  be  seen  shaped  like  a 
dumb-bell,  half  of  it  through  the  wall  of 
the  blood  vessel  and  half  still  in  the 
blood  vessel.  After  the  corpuscle  is 
out,  no  hole  can  be  found  to  account 
for  its  mysterious  passage.  The  white 
corpuscles  consist  of  protoplasm.  The 
red  corpuscles  contain  no  protoplasm. 
Hence  the  latter  arc  not  really  alive. 

The  Use  of  Each  Part  of  the  Blood.— 
The  plasma  keeps  the  blood  in  a  liquid 
state,  so  that  it  may  flow  readily ;  the 
plasma  also  transports  the  food  that  has 
been  eaten  and  digested,  and  carries  carbon  dioxid  to  the 
lungs  and  other  waste  material  to  the  kidneys.     The  red 


Fig.  6o.  —  Human  Blood  Cells  (magni- 
fied 40,000  areas),  showing  many  red  cells 
and  a  single  white  blood  cell  on  left,  larger 
than  red  cells.     (Peabody.) 


Fig.  61.  — Side  and 
Front  Views  of 
Frog's  and  Man's 
Red  Corpuscles, 
drawn  to  same 
scale.  Compare 
outline,  concavity, 
diameters. 


60  HUMAN  BIOLOGY 

corpuscles  transport  the  oxygen  from  the  lungs  to  the  tis- 
sues. The  white  corpuscles  devour  and  destroy  irritating 
particles,  such  as  drugs,  poisons,  and  germs.  They  are  of 
great  importance  in  purifying  the  blood  and  as  a  protec- 
tion against  disease.     One  is  shown  in  Fig.  60. 

The  sounds  of  the  heart  beat  may  be  heard  by  applying 
the  ear  to  the  chest.  They  are  two,  a  long,  dull  sound  and 
a  short,  clear  one.  The  first  comes  from  the  vibration  of 
the  bicuspid  valve  together  with  an  unexplained  tone  aris- 
ing from  large  contracting  muscles,  in  this  case  the  walls 
of  the  ventricles.  The  second,  or  short,  clear  sound,  is 
produced  by  the  sudden  closing  and  vibration  of  the  semi- 
lunar valves. 

Changes  in  the  Composition  of  the  Blood  as  it  passes 
through  the  Various  Organs.  —  When  the  blood  is  forced 
out  by  the  heart,  part  of  it  goes  to  the  stomach  and 
intestines  through  arteries  which  divide  into  capillaries. 
These  capillaries  absorb  all  kinds  of  food  from  the  ali- 
mentary canal  except  the  fats  (see  p.  64),  and  unite  to 
form  the  portal  vein,  which  takes  the  absorbed  food  to  the 
liver.  In  the  liver  some  of  the  impurities  of  the  blood  are 
burned  up  and  changed  into  bile.  The  blood,  purified  and 
laden  with  food,  is  carried  from  the  liver  to  the  heart,  where 
it  reenters  the  general  blood  stream.  The  blood  flow  from 
the  food  tube  through  portal  vein  and  liver  to  the  heart,  as 
just  described,  is  called  the  Portal  circulation. 

Renal  circulation.  Two  branches  from  the  aorta  carry 
blood  to  the  kidneys.  There  the  urea  and  a  large  amount 
of  water  are  taken  out,  and  the  purified  blood  is  emptied 
into  the  large  vein  that  leads  up  to  the  heart. 

Pulmonary  circulation  (Fig.  67).  This  is  the  circulation 
through  the  lungs.  During  this  circulation  carbon  dioxid 
gas  is  removed  from  the  blood  and  oxygen  is  added  to  it. 


THE    CIRCULATION 


6l 


Fig.  62.  —  Blood  Clot 
separated  from  serum. 


Some  impurities  and  a  large  amount  of  water  escape 
from  the  blood  as  it  passes  through  the  skin. 

Coagulation.  —  So  long  as  blood  is  in  an  uninjured  blood 
vessel  it  remains  a  liquid.  In  a  few  minutes  after  it  flows 
from  a  blood  vessel,  it  forms  into  a 
stiff,  jelly  like  mass  called  a  clot  (Fig. 
62).  The  process  of  forming  the  clot 
is  called  coagulation,  and  it  is  brought 
about  by  the  albuminous  substance 
called  fibrin,  which  is  always  in  the 
plasma  of  healthy  blood.  On  expos- 
ure to  air  the  fibrin  forms  into  a  net- 
work of  fine  threads  throughout  the 
mass  (Fig.  63)  and  the  corpuscles  become  entangled  in  the 
meshes.  The  clot  consists  of  the  fibrin  of  the  plasma  and 
corpuscles ;  the  watery  portion  of  the  plasma,  called  the 
serum,  separates  from  the  clot  (Fig.  62).     The  property  of 

coagulating  is  a  great  safe- 
guard, as  a  clot  often  plugs 
up  a  cut  blood  vessel.  What 
is  the  difference  between  se- 
rum and  plasma? 

Veins  and  Arteries  com- 
pared. —  The  veins  have  thin, 
soft  zvalls  and  the  arteries 
have  thick,  tough,  elastic  zvalls. 
When  a  vein  is  cut,  it  may 
usually  be  closed  by  pinching 
the  walls  of  the  end  together. 
If  an  artery  is  cut,  the  walls  zvill  not  readily  stick  together, 
but  often  stand  open  until  the  end  of  the  artery  is  tied. 
For  this  reason,  and  because  an  artery  is  subject  to  the 
direct  pressure  of  the  heart,  a  cut  artery  is  more  dangerous 


Fig.  63.  — Network  of  Fibrin  in 
Human  Blood  (enlarged). 


62  HUMAN  BIOLOGY 

to  life  than  a  cut  vein.      Because  of  the  toughness  of  the 

arteries,  and  because  they  are  located  close  to  the  bones, 
they  are  less  likely  to  be  cut  than  the  veins,  which  are 
softer  and  nearer  the  surface.  The  veins  begin  in  capil- 
laries and  empty  into  the  auricles ;  the  arteries  begin  at  the 
ventricles  and  empty  into  capillaries ;  and  there  is  a  semi- 
lunar valve  at  the  origin  of  each  artery. 

Cuts  and  Bruises.  —  i.  Wash  a  cut  under  running  water. 
2.  Stop  the  bleeding.  The  washing  in  cold  water  may  do 
this.  Elevating  an  injured  arm  or  leg  will  aid  the  blood 
greatly  in  forming  a  clot  at  the  opening.  3.  Bandage 
firmly  with  a  strip  of  cloth  and  sew  the  end.  Keep  wet 
the  part  of  the  bandage  where  the  cut  is  ;  this  lowers  the 
temperature  of  the  wound.  It  may  be  necessary  to  hold 
a  gaping  wound  closed  with  strips  of  surgeon's  plaster 
placed  across  the  cut.  A  handkerchief  folded  first 
into  a  triangle  and  then  into  a  narrow  bandage  is  often 
useful.  A  cut  artery  may  be  known  from  a  cut  vein  by 
the  brighter  color  of  the  blood,  and  by  the  flow  being 
stronger  at  each  heart  beat,  while  the  flow  from  a  vein  is 
uniform.  Pressure  to  stop  the  flow  of  blood  from  an 
artery  should  be  applied  between  the  cut  and  the  heart; 
but  when  the  blood  comes  from  a  vein,  the  pressure  should 
be  applied  to  the  side  of  the  cut  farthest  from  the  heart. 

Apply  hot  water  immediately  for  several  minutes  to  a 
bruise.  Either  a  bruise  or  a  cut  may  be  washed  with  a  weak 
solution  of  some  antiseptic  such  as  carbolic  acid.  After 
washing  a  bruise  it  may  be  bound  with  a  cloth  soaked  in 
witch  hazel  or  arnica. 

The  Lymphatic  System 

This  system  contains  and  conveys  a  liquid  called 
the   lymph.      It   consists    of    lymph   spaces,  lymph   tubes, 


THE    CIRCULATION 


63 


(lymphatics),  and  lymphatic  glands.  Lymph  corresponds 
nearly  to  the  blood  without  the  red  corpuscles.  It  is  the 
familiar  liquid  seen  in  a  blister,  or  oozing  out  where  the 
skin  has  been  grazed  without  breaking  a  blood  vessel. 

Necessity  for  Lymph  and  Lymph  Spaces.  —  The  body 
cannot  be  nourished  with  the  albumin,  sugar,  oxygen,  and 
other  digested  food  in  the  blood,  until  this  food  passes  out 
of  the  blood  vessels.  The  food  leaves  the  blood  through 
the  thin  walls  of  the  capillaries.  Many  of  the  cells  do  not 
touch  the  capillaries,  and  the  lymph  penetrates  the  spaces 
between  the  cells  to  reach  them  (see  colored  Fig.  3).  If 
there  were  no  lymph  spaces,  these  cells  could  not  get  any 
food.  The  lymph  bathes  the  cells,  and  the  cells  absorb 
what  they  want  from  the  nourishing  fluid.  The  red  corpus- 
cles bearing  the  oxygen  cannot  pass  through  the  capillary 
walls.  Oxygen,  being  a  gas,  readily  passes  through  the 
walls  and  reaches  the  cells  through  the  lymph  in  the 
lymph  spaces.  The  waste  materials  must  go  back  into  the 
blood ;  carbon  dioxid  passes  back  through  the  capillary 
walls  and  is  taken  to  the  lungs ;  how  the  other  waste 
materials  formed  in  the  cells  pass  back  will  soon  be 
explained. 

Need   of  Lymphatics.  —  The  plasma   continually  passes 

into  the  tissues,  but  it  cannot  return  directly  into  the  blood. 

The    lymph    contains    waste     material    which    must    be 

removed,  and  also  much  unused  food  which  nature,  like  an 

economical  housekeeper,   will  offer  to  the  tissues   again. 

There  are  vessels  called  lymphatics  that  take  the  lymph  back 

into  the  blood  (see  Fig.  64). 

The  Lymphatic  Circulation  (Fig.  64).  —  The  blood  flow  does  not 
begin  nor  end.  but  makes  a  never  ending  circle.  The  countless 
lymphatics  begin,  with  open  ends.  1/1  the  lymph  spaces  between  the  cells 
(colored  Fig.  3).  The  smaller  lymphatics  unite  into  larger  ones  until 
finally  they  all  unite  into  two  large  ones  that  empty  into  the  large  veins 


64 


HUMAN  BIOLOGY 


under  the  collar  bones,  near  the  neck.     The  one  that  empties  under  the 
left  collar  bone  (3,  Fig.  66)  is  called  the  thoracic  duct  because  it  goes 


Fig.  64.  — Surface  Lymphatics  of  Hand. 

up  through  the  thorax  just  in  front  of  the  spinal  column  (1.  Fig.  66). 
The  other  at  the  right  side  of  the  neck  is  called  the  right  lymphatic 
duct  (see  Figs.  64,  65). 

In  persons  with  the  dropsy,  the  lymph  accumulates  in  the  lymph 
spaces  and  is  not  drained  away  by  the  lymph  flow.  Dropsy  usually 
shows  itself  first  by  swelling  of  the  feet  and 
the  leg  below  the  knee.  (Why  ?  See  Exp.  2.) 
There  is  a  set  of  lymphatics  called  lacteals, 
situated  in  the  abdomen,  which  have  the  func- 
tion of  absorbing  digested  fats  from  the  intes- 
tine (Figs.  66,  100,  and  colored  figure  2). 

What  makes  the  Lymph  Flow  ?  —  The  heart 
does  not,  for  its  pressure  is  not  transmitted  be- 
yond the  blood  tubes.  The  successive  pressures 
of  a  working  muscle  move  the  lymph  forward 
in  the  lymphatics  in  the  same  way  that  the  blood 
is  moved  forward  in  the  veins,  and  the  valves 
keep  it  from  moving  back.  When  riding  a  trot- 
ting horse,  or  in  a  jolting  vehicle,  the  lymph  is 
moved  beyond  the  valves  at  every  jolt  (Fig. 
64).  Without  exercise  the  lymph  stagnates, 
and  the  body  becomes  poisoned  by  its  own 
wastes.  At  every  expansion  of  the  lungs  lymph 
and  it  is  forced  out  of  the  chest  at  every  con- 
traction. Deep  breathing  is  as  great  a  benefit  to  the  body  in  moving 
stagnant  lymph  as  it  is  in  purifying  the  blood. 


Fig.  65.  —  Diagram  to 
show  the  two 
Parts  of  the  Body 
drained  by  the 
Two  Lymph  Ducts. 

is  drawn  into  the  chest 


THE    CIRCULATION 


65 


The  lymphatic  glands  are  kernel-like  enlargements 
along  the  lymphatics,  and  they  contain  a  great  many 
lymph  cells  which  purify  the  lymph  as  it  passes  through 


Fig.  66.  — Chief  Lymphatic  Vessels  and  Glands  of  trunk. 

i,  3,  Thoracic  duct  (emptying  at  3) ;  2,  receptacle  for  chyle  (lacteals  below  it). 

them.  The  lymphatic  glands  are  numerous  in  the  armpits 
and  the  groins.  The  cells  in  the  lymph  glands  multi- 
ply, and  some  of  them  are  carried  by  the  lymph  into 
the  blood  to  become  those  remarkable  little  bodies,  the 
white  corpuscles. 


66  HUMAN  BIOLOGY 


Hygiene   of   the    Circulati 


on 


Effects  of  Work,  Fresh  Air,  and  Rest  on  Corpuscles  and 
Plasma. —  Work  uses  up  the  nutritious  elements  in  the 
blood.  A  few  hours  after  food  is  eaten  the  nutritious  ma- 
terials in  the  blood  are  found  to  be  increased.  By  the 
breathing  of  fresh  air  the  carbon  dioxid  in  the  plasma  is 
diminished  and  the  oxygen  in  the  colored  corpuscles  is  in- 
creased, changing  the  blood  to  a  brighter  red.  Sleep  gives 
time  for  the  exhausted  cells  and  depleted  blood  to  be  re- 
plenished. Loss  of  sleep  means  longer  hours  of  activity 
and  greater  consumption  of  nutriment  with  shorter  hours 
for  replacing  the  nutriment.  The  pale  skin  of  one  who  has 
lost  sleep  tells  of  the  exhausted  condition  of  the  blood. 

How  the  Muscles  help  the  Circulation.  — The  imperative 
need  of  muscular  exercise  to  keep  the  body  sound  exists 
because  of  the  lack  of  other  means  to  cause  movement  in 
the  veins  and  lymphatics.  Good  food,  pure  air,  and  plenty 
of  exercise  are  necessary  for  healthy  blood.  Many  so- 
called  "blood  purifiers"  are  advertised  to  entrap  the 
ignorant.  It  is  impossible  to  imagine  how  "  blood  puri- 
fiers "  can  aid  the  blood.  The  blood  is  'purified,  not  by 
putting  anything-  into  the  blood,  but  by  something  going  out 
of  it  as  it  passes  through  the  skin,  kidneys,  liver,  and  lungs. 
These  organs  all  send  out  impurities  brought  to  them  by 
the  blood. 

The  one  great  hygienic  effect  of  muscular  exercise  is  an 
active  circulation,  and  from  an  active  circulation  nine  chief 
effects  may  be  traced.  The  effects  upon  the  body  will  be 
given  in  order,  beginning  with  the  surface — skin,  fat, 
muscles,  bones ;  and  the  effects  upon  the  internal  organs 
are  given  in  order  of  position,  beginning  with  the  highest 
—  brain,  lungs,  heart,  digestive  organs. 


THE    CIRCULATION  6 J 

Effects  of  Exercise  and  Improved  Circulation. —  i.    The 

skin  is  made  fresh,  pink,  and  smooth  from  the  flushing  of 
the  capillaries ;  it  is  purified  by  the  perspiration  and  the 
renewal  of  cells.  2.  If  the  fat  is  too  great  in  amount,  it  is 
burned  up ;  if  it  is  too  small  in  amount,  the  better  nourish- 
ment brought  by  the  blood  increases  it.  3.  The  muscles 
are  better  fed  (see  Fig.  48)  and  grow  firm,  strong,  and 
large.  4.  The  skeleton  is  held  in  proper  position  by  the 
stronger  muscles,  and  deformity  is  prevented.  5.  The 
brain.  The  pure,  fresh  blood,  loaded  with  oxygen  from 
expanded  lungs,  flushes  every  capillary  of  the  brain,  clears 
the  mind,  and  doubles  or  trebles  its  power  to  work. 
6.  The  lungs  are  expanded  by  deep  breathing  if  the  exer- 
cise be  rapid  and  vigorous.  A  slow  stroll  or  saunter  is  not 
of  value.  7.  The  circulation.  Every  contracting  muscle 
aids  the  heart  in  its  work.  The  deep  breathing  moves 
stagnant  lymph.  8.  The  stomach.  Exercise  burns  up  the 
food  and  increases  the  appetite.  9.  General  effects.  Ex- 
ercise promotes  good  humor,  decreases  loafing,  cigarette 
smoking,  gossiping,  and  other  vices. 

The  effect  of  tobacco  on  the  heart,  if  cigarettes  or 
cigars  are  used,  is  sometimes  to  cause  attacks  of  irregular 
beating ;  the  heart  flutters  faintly  for  a  while,  then  palpi- 
tates strongly,  then  flutters  again.  This  condition  is  called 
tobacco  heart,  or  trotting  heart. 

Effect  of  Alcohol  upon  the  Circulation. — After  a  person 
has  taken  an  alcoholic  drink  his  face  and  skin  are  likely  to 
become  flushed,  and  perhaps  his  heart  beats  faster.  Most 
investigators  have  found  that  the  alcohol  itself  does  not 
directly  increase  or  strengthen  the  action  of  the  heart. 
Hence  it  is  probably  wrong  to  call  alcohol  a  heart  stimu- 
lant. The  flushing  of  the  skin  is  believed  to  be  due  to  the 
relaxing   effect   of  alcohol.     It  relaxes,  it    paralyzes,   the 


68  HUMAN  BIOLOGY 

vasomotor  nerves  which  control  the  little  muscle  fibers 
in  the  walls,  of  the  blood  vessels.  The  relaxing  and 
enlarging  of  the  blood  vessels  decreases  the  resistance  to 
the  blood  flow,  and  the  heart  beats  faster  under  its  lighter 
load.  The  narcotic  effect  of  alcohol  is  much  more  power- 
ful than  its  irritating  or  stimulating  effect.  The  effect 
of  alcohol  in  causing  fatty  degeneration  of  the  muscles 
often  weakens  the  heart  and  other  blood  vessels. 

Climate  and  Brain  Work,  r-  /;/  going  to  sleep  the  vessels  in  the  skin 
dilate  and  blood  is  drawn  from  the  brain  to  the  skin.  It  is  difficult  to 
go  to  sleep  when  cold,  for  cold  sends  the  blood  to  the  brain  and  keeps 
the  mind  active.  On  the  same  principle,  mental  work  is  difficult  in  very 
warm  weather  because  of  the  enlarged  capillaries  in  the  skin  and  the 
withdrawal  of  blood  from  the  brain  to  the  skin.  This  increases  the 
perspiration  and  keeps  the  temperature  of  the  body  down  to  normal,  but 
it  deprives  the  brain  of  blood  needed  for  good  mental  work.  Mental 
workers  in  warm  weather  and  in  warm  climates  should  seek  every  con- 
dition favoring  coolness.  Benjamin  Franklin  was  accustomed  to  strip 
himself  almost  entirely  of  clothing  when  he  was  writing  and  wanted  his 
brain  to  work  at  its  best.  The  wearing  of  barefoot  sandals  and  the  thin- 
nest cotton  clothing,  light  in  color,  helps  to  prevent  mental  inertia  in  hot 
weather.  In  the  Gulf  states  in  summer  and  in  our  tropical  islands  the 
best  mental  work  can  be  done  by  rising  at  dawn  and  working  before 
the  hot  part  of  the  day  begins.  Some  of  the  greatest  thinkers  in  the 
world  have  lived  in  warm  climates  (Greece  and  India),  but  they  wore 
very  few  clot  lies  and  ate  moderately  of  the  simplest  food  (see  p.  44). 

Congestion  is  a  swelling  of  the  blood  vessels  of  some  part,  with  the 
accumulation  of  blood  therein.  Congestion  is  active  when  a  rapid  flow 
of  blood  distends  the  capillaries.  Example,  flushing  of  face  when 
running.  Congestion  is  passive  when  there  is  a  narrowing  of  the  out- 
let of  the  capillaries,  the  blood  moves  slowly  and  partly  stagnates  in  the 
swollen  vessels.  Example,  when  the  nose  feels  stopped  up  during  a 
cold.  If  a  syringe  is  worked  so  fast  that  the  rubber  tube  swells,  this  is 
like  active  congestion ;  if  the  end  of  the  tube  is  pinched  together  so 
that  moderate  pumping  causes  it  to  swell,  this  is  like  passive  con- 
gestion. 

Inflammation  is  congestion  where  the  vessels  of  any  part  are  strained 
and  injured.  White  corpuscles  collect  there  to  repair  the  vessels  and 
devour  the  blood  that  escapes  and  stagnates  there.  They  also  destroy 
germs  that  have  usually  found  lodgment  and  begun  to  multiply.     The 


THE    CIRCULATIOX  69 

serum  of  the  blood  also  destroys  the  germs  by  the  antitoxins  in  it. 
Inflammatory  troubles  are:  colds,  rheumatism,  diarrhoea,  and  all  dis- 
eases with  name  ending  "#&."  An  inflamed  part  is  red,  swollen,  hot, 
and  painful. 

Prevention  and  Care  of  Colds.  —  A  cold  is  an  inflammation  of  a 
mucous  membrane.  Colds  are  prevented  by  so  living  as  to  encourage 
'a.  free,  vigorous  circulation,  and  especially  by  not  coddling  the  body  so 
tenderly  that  the  circulation  becomes  deranged  by  the  least  exposure. 
The  circulation  may  be  deranged  by  overheating  as  well  as  by  chilling 
the  body ;  usually  it  would  be  more  appropriate  to  say  that  the  person 
caught  '•  a  hot  "  than  ■'  a  cold."  At  the  first  sign  of  a  cold  vigorous 
exercise,  a  cold  bath,  or  going  outdoors  into  cold  air  may  aid  in  sending 
fresh  blood  to  remove  the  stagnation  and  stop  the  inflammation.  A 
warm  foot  bath  and  hot  drinks  may  relieve  by  drawing  blood  from  the 
congested  mucous  membrane.  After  the  cold  has  become  fixed  such 
measures  will  not  help,  but  the  cure  is  aided  by  helping  the  skin  to 
keep  its  full  share  of  blood.  The  cold  must  run  its  course.  The  cells 
will  be  given  every  chance  to  repair  the  injury  and  destroy  the  germs 
(if  any)  by  avoiding  hard  work,  eating  moderately  of  digestible  food, 
avoiding  drugs,  especially  infallible  drugs  advertised  in  newspapers, 
even  if  recommended  by  otherwise  intelligent  people.  Repeated  colds 
tend  to  become  a  disgusting  disease  called  chronic  catarrh.  Con- 
stricting the  blood  vessels  of  the  skin  causes  congestion  of  the  (internal) 
mucous  membranes.  A  skin  tenderly  protected  constricts  more  readilv 
than  one  accustomed  to  cold.  Cold  is  the  best  preventive  of  cold.  Cold 
baths,  pure  air,  light  clothing,  free  breathing,  moderate  eating,  ward  off 
colds.  Fussing  with  sprays,  gargles,  and  drugs  will  not ;  for  the 
main  factor  in  bringing  on  a  cold  is  not  germs,  nor  temperature,  but  the 
state  of  the  system  itself.  Persons  who  have  suffered  much  with  colds 
have  found  that  after  substituting  cotton  underwear  for  woolen,  colds 
became  very  rare.  Linen  will  have  a  similar  effect,  but  it  is  not  as  dur- 
able, soft,  or  heat-retaining  as  cotton  (see  p.  16). 

Practical  Questions.  —  1.  Through  what  kind  of  skin  do  the 
blue  veins  in  the  wrist  show  most  plainly?  2.  Which  is  more  com- 
pressible, a  vein  or  an  artery?  3.  Why  are  those  who  take  little  exer- 
cise likely  to  have  cold  feet?  (p.  57.)  4.  Where  does  the  so-called 
venous  blood  flow  through  an  artery?  5.  What  vein  begins  and 
ends  in  capillaries?  (The  portal  vein,  colored  Fig.  5.)  6.  To  what 
purifying  organ,  after  leaving  the  lungs,  does  the  heart  send  part  of 
the  blood  for  further  purification.  (Colored  Fig.  5.)  7.  What  keeps 
the  blood  moving:  between  the  beats  of  the  heart? 


CHAPTER   VI 

THE   RESPIRATION 

Experiment  i.  (Home.)  Study  of  the  Throat.  —  Sit  with  the  back 
to  the  light.  Study  the  open  mouth  and  throat  with  a  mirror  and  make 
out  the  uvula,  tonsils,  and  other  parts  shown  in  Fig.  68. 

Experiment  2.  Anatomy  of  Lungs.  —  Study  fresh  lungs  of  sheep, 
hog.  fowl,  or  frog.  Will  they  float  ?  Will  they  contract  when  expanded 
by  air  blown  in  through  a  quill  or  other  tube?  What  is  the  structure 
of  the  windpipe?  Can  you  distinguish  the  arteries  from  the  veins  by 
the  stiffness  of  their  walls?  Which  contain  pure  blood?  Study 
branching  of  air  tubes.     Make  a  sketch. 

Experiment  3.  Tests  of  Expired  Air. —  Breathe  upon  a  mirror,  bright 
knife  blade,  or  cold  window  pane.  Result?  State  your  conclusion? 
Experiment  4 —  Carbon  dioxid  added  to  limewater  will  cause  a  white 
cloud  consisting  of  particles  of  limestone.  Breathe  through  a  tube  or 
straw  or  the  hollow  stem  of  a  reed  into  clear  limewater.  Result?  Con- 
clusion? (Limewater  may  be  had  at  druggist's  or  made  by  pouring 
water  upon  a  lump  of  unslackened  lime  and  draining  it  off  when  lime 
has  settled.)  Experiment  5.  Breathe  for  several  minutes  upon  the 
bulb  of  a  thermometer.  Result?  Conclusion?  Experiment  6.  Breathe 
a  few  times  into  a  large,  carefully  cleaned  pickle  jar,  or  a  bottle.  Cork 
it  tightly,  and  set  it  in  a  warm  place  for  several  days.  Then  uncork 
and  smell  the  air  in  it.  Result?  Conclusion?  Experiment  7.  Pierce 
a  small  hole  in  a  card,  place  card  over  a  wide-mouthed  bottle,  and 
breathe  into  bottle  through  a  tube,  lemonade  straw,  or  hollow  reed. 
Pull  out  straw.  Place  bottle,  mouth  downward,  on  table,  and  slip  out 
card.  Slide  bottle  to  edge  of  table  and  lift  lighted  candle  into  bottle. 
Result?  Experiment  8.  Place  bottle  of  fresh  air  over  lighted  candle. 
Result?     Conclusion?     (See  Animal  Biologv,  p.  14.) 

Experiment  9.  (School.)  Testing  the  Air  of  a  Room.  — Fill  a  fruit 
jar  or  large  bottle  with  water,  and  take  it  into  a  room  containing  many 
people.  Pour  out  the  water.  (This  insures  that  all  the  air  now  in  the 
jar  is  air  obtained  in  the  room  to  be  tested.)  Seal  the  jar  if  test  is  not  to 
be  made  at  once.  Test  by  pouring  in  two  tablespoonfuls  of  clear  lime- 
water  and  shake.     If  the  limewater  turns  milky,  the  ventilation  is  bad. 

Experiment  10.  (Home  and  school.)  Homemade  Current  Detector. — 
Dangle  a  bit  of  paper  by  means  of  a  spider  web  or  thread  from  the 

70 


THE  RESPIRATION  J\ 

end  of  a  walking  stick  or  ruler.  (Or  test  with  the  flame  of  a  candle.) 
Hold  it  near  cracks  of  window,  above  and  below  doors,  and  especially 
before  openings  intended  for  entry  and  exit  of  air,  and  test  if  air  moves 
as  desired. 

Experiment  II.  Ventilation  of  the  Schoolroom.  —  Let  the  whole 
class  rise,  and  with  the  fingers  test  cracks  around  doors  and  windows. 
Wherever  the  air  feels  cold  to  the  hand  the  air  is  entering. 

Experiment  12.  Dust.  —  With  a  mirror  cause  a  sunbeam  to  play  like 
a  search  light  into  a  closed  room  several  hours  after  it  has  been  swept. 
Result?  Do  the  same  in  a  room  where  every  window  and  door  were 
open  during  sweeping  and  left  open  afterwards.  Result?  Conclusion? 
Note  also  the  amount  of  dust  on  the  furniture  of  each  room. 

Experiment  13.  Study  of  Habitual  Quiet  Breathing.  — Without  any 
more  disturbance  of  the  breathing  than  can  be  helped,  direct  your  atten- 
tion to  your  breathing  while  sitting  quietly.  Record  motions  of  any 
parts  of  chest  and  abdominal  walls  that  may  be  noticeable.  If  neces- 
sary, lay  the  hands  successively  against  different  parts  of  the  wall  to 
test  for  motion.     Think  of  another  subject,  and  later  repeat  observations. 

Experiment  14.  Study  of  Deep  Breathing.  —  Place  your  hands  suc- 
cessively upon  the  front  and  sides  of  your  chest,  waist,  and  abdomen, 
while  drawing  in  and  sending  out  deep  breaths.  What  motions  of  the 
several  parts  are  observed  at  each  stage? 

Experiment  15.  Study  of  Elasticity  as  a  Factor  in  Breathing. — 
(1)  Notice  whether  in  quiet  breathing  there  is  an  elastic  rebound  as 
the  breath  goes  either  in  or  out.  If  so,  it  is  due  to  the  elasticity  of  the 
cartilages  or  air  cells  of  lungs,  or  both.  (2)  Breathe  by  inflating  the 
lungs  strongly  at  each  breath.  Is  the  air  then  forced  out  without 
effort?  (3)  Breathe  by  flattening  the  chest  and  abdomen  as  much  as 
possible  at  each  breath.     Does  the  air  then  rush  in  without  effort? 

Experiment  16.  Chest  Breathing.  —  Try  to  breathe  wholly  by  deep 
expansions  and  contractions  of  chest  wall.  What  motions,  if  any.  are 
noticed  in  abdominal  wall  as  breath  goes  in?  As  it  goes  out?  (Test 
motions  with  hand.) 

Experiment  17.  Abdominal  Breathing.  — Try  to  hold  the  chest  walls 
still  and  breathe  by  strong  contraction  and  expansion  of  abdomen. 
Do  the  chest  walls  move  at  all?  Neither  "chest  breathing''  nor 
'•  abdominal  breathing  "  is  the  normal  way.     See  text. 

Experiment  18.  Full  Breathing. — Try  breathing  by  outward  and 
inward  movement  of  walls  of  chest,  waist,  and  abdomen.  Do  you  suc- 
ceed? This  is  normal  breathing.  Is  the  motion  greater  at  the  front 
or  the  sides  of  the  waist?  Put  a  belt  around  the  waist  tight  enough  to 
stay  in  place  and  repeat.     Is  the  waist  motion  interfered  with  ? 


7 2  II UMAX  BIOLOGY 

Experiment  19.  How  the  Ribs  are  Lifted.  —  Make  a  model  like 
sketch  to  represent  backbone,  breastbone,  and  two  ribs,  using  pins  to 
make  joints  loose  at  corners.  Use  cords  for  diagonals. 
What  happens  when  cord  ac  is  pulled?  When  cord 
Mis  pulled?  The  cords  correspond  to  the  two  sets 
of  muscles  between  the  ribs. 

Experiment  10.  Study  of  Laughing. — Place  the 
hands  upon  the  waist  and  abdomen  when  laughing. 
What  motion  occurs  at  each  sound  of  laugh?  Draw 
in  the  abdominal  wall  with  a  jerk.  What  is  the  effect 
upon  the  breath  ? 

Experiment  2 1 .  Modifications  of  the  Breath.  — 
Write  I,  E,  or  IE  after  each  word  in  this  list,  accord- 
ing as  inspiration,  expiration,  or  both,  are  involved  in  the  action.  (Test 
with  sham  acts  if  possible.)  Sighing,  sobbing,  crying  (of  a  child), 
coughing,    laughing,    yawning,    sneezing,    hiccoughing,    snoring. 

Experiment  22.  Effects  of  Exercise.  —  Count  and  record  the  rates  of 
breathing  before  and  after  vigorous  exercise. 

Experiment  23.  Comparative  Study.  —  Observe  and  record  the  rate 
and  manner  of  breathing  of  cow,  horse,  dog,  cat,  etc.  Is  the  air  drawn 
in  or  sent  out  more  quickly?  Is  there  a  pause?  If  so,  after  which  stage 
of  breathing? 

Experiment  24.  Emergency  Drill.  —  Resuscitation  from  drowning, 
etc.     See  Coleman's  "Elements  of  Physiology,"  page  356. 

Necessity  for  Breathing  and  for  Specialized  Organs  of 
Breathing.  —  The  body  is  a  self-regulating  machine  which 
possesses  energy.  This  energy,  like  that  of  steam  engines, 
arises  from  oxidation  which  takes  place  continually,  but  at 
a  varying  rate.  Food  for  fuel  is  taken  at  intervals,  but 
oxygen  must  be  taken  in  continually.  Man  breathes  about 
eighteen  times  per  minute.  The  blood  in  the  tissues  soon 
becomes  dark  because  of  loss  of  oxygen  and  absorption  of 
carbon  dioxid.  It  is  then  pumped  through  the  heart  to 
the  organ  which  has  the  function  of  absorbing  oxygen 
and  giving  off  carbon  dioxid  (Fig.  6j).  In  some  animals, 
as  the  ameba  and  the  earthworm,  the  surface  of  the  body 
suffices  for  breathing.  This  cell  breathing  is  the  true 
essential  respiration ;  it  is  universal  among  living  things, 


THE   RESPIRATION 


73 


both  plants  and  animals.  To  supply  the  deeper  cells  large 
animals  require  a  breathing  surface  greater  than  the  area 
of  the  skiu.  This  is  supplied  by  having  the  oxygen-absorb- 
ing surface  folded  inward  to  form  folds,  tubes,  and  cavities 
of  great  complexity.  If  the  lungs  of  a  man  were  unfolded 
and  all  their  tubes  and  cavities  spread  upon  one  surface, 
an  area  of  more  than  one  hundred  square  feet  (or  ten  feet 
square)  would  be  covered. 

Each  respiration,  or  breath,  consists  of  the  passing  in 
of  the  air,  or  inspiration,  sending  it  out,  or  expiration, 
and  a  pause  after 
one  but  not  after 
both  of  the  other 
stages. 

The  Air  Passages. 
—  The  air  usually 
passes  in  at  the 
nose  and  returns 
by  the  same  way, 
except  during  talk- 
ing or  singing.  Ob- 
serve your  mouth 
with  a  mirror  (Fig. 
68);  at  the  back 
part,  an  arch  is 
seen  which  is  the 
rear  boundary  line 
of  the  mouth  (Exp. 
i).  Just  above  the 
arch  is  likewise  the  rear  boundary  line  of  the  nasal  pas- 
sages. The  funnel-shaped  cavity  beyond,  into  which  both 
the  mouth  and  nasal  passages  open,  is  called  the  pharynx 
(far'inks),  or  throat  (see  Fig.  68,  also  Fig.  83).     Below, 


Fig.  67.  —  Circulation  through  Lungs  (sche- 
matic) :  "venous"  blood  (in  pulmonary  artery) 
black;  "arterial"  blood  (in  pulmonary  veins) 
white. 


74 


HUMAN   BIOLOGY 


Fig.  68.  — Open  Mouth,  showing  palate  and  tonsils. 


two  tubes  open 
from  the  phar- 
ynx. One  is  the 
1  rac hca  (tra'kea) 
or  windpipe,  the 
other  is  the  esoph- 
agus or  gullet. 
At  the  top  of  the 
trachea  is  the 
cartilaginous  lar- 
ynx, or  voice  box. 
If  the  finger  is 
placed  upon  the 
larynx  or  Adam's 
apple,  it  is  plainly 
felt  to  move  up 
and  down  when 
swallowing.  The  opening  into  the  larynx  is  provided  with 
a  lid  of  cartilage,  the  epiglottis.     Inside  the  larynx,  the 

vocal  cords  are  stretched 
from  front  to  back.  Just 
below  the  larynx  comes  the 
trachea  proper,  which  is  a 
tube  about  three  fourths  of 
an  inch  in  diameter  and 
about  four  inches  long  (Fig. 
69).  It  consists  of  hoops  of 
cartilage  (Fig.  69)  which  are 
not  complete  circles,  but  are 
shaped  somewhat  like  the 
letter  C,  being  completed  at 

FIG.  69.  —  Lungs,  P\  with  trachea,         .1  1  i 

rJ  *.      j   1    a.i   1  1         the  rear  by  involuntary  mus- 

TA;  thyroid  gland,  th\  larynx,  I.;  J  -' 

and  hyoid  bone,  h.  cular  tissue,  whose  function 


p— 


THE   RESPIRATION 


75 


Fig.  70.  —  Lobule 
of  Lung. 


is  to  draw  the  ends  together  at  times  (for  instance,  during 
coughing)  and  reduce  the  size  of  the  tube.  The  function 
of  the  hoops  of  cartilage  is  to  keep  the  windpipe  open  at 
all  times.  If  it  should  be  closed  by  pressure,  life  might 
be  lost.  These  rings  of  cartilage  may  be  felt  in  the  neck. 
The  lower  end  of  the  trachea  is  just  behind  the  upper 
end  of  the  breastbone;  there  it  divides  into  two  large 
tubes.  These  subdivide  into  a  great 
number  of  smaller  branches  called  bron- 
chial tubes.  Cartilage  is  found  in  the 
walls  of  all  but  the  smallest  of  the  tubes. 
The  subdivision  continues,  somewhat  like 
the  branching  of  a  tree,  until  the  whole 
lung  is  penetrated  by  bronchial  tubes. 
Each  tiny  tube  finally  ends  in  a  wider 
funnel-shaped  chamber  called  a  lobule 
(Fig.  70),  into  which  so  many  dilated 
sacs,  called  air  cells,  open,  that  the  walls  of  the  terminal 
chamber  or  lobule  may  be  said  to  consist  of  tiny  cups,  or 

air  cells,  placed  side  by 
side.  The  lobules,  or 
clusters  of  air  cells,  are 
chiefly  near  the  surface 
of  the  lung.  (The  word 
"  cell  "  is  here  used  in 
its  original  sense  to  de- 
note a  cavity  or  cham- 
ber, and  not  in  the  sense 
of  a  protoplasmic  cell.) 
The  air  cells  are  elastic 

Fig.  71.  — Capillaries  around  Air  Sacs       and   enlarge   by  stretch- 
OF  LUNGS  (enlarged  30  diameters).     Air        •  ag      the      chegt      ^ 

sacs  in  white  spaces.    Dark  lines  are  capil-  ° 

laries.    (Peabody.)  pands ;  hence,  the  cells 


76 


11 1  MAX  BIOLOGY 


must  have  many  of  the  yellow  elastic  fibers  of  connective 
tissue  in  their  walls.  They  are  lined  with  an  exceedingly 
thin  membrane  of  epithelial  cells  through  which  oxygen 
and  carbon  dio.x  id  arc  exchanged.  In  the  walls  of  the  air 
cells  there  is  a  network  of  capillaries  (Fig.  71).  The  dark 
red  blood  comes  into  these  capillaries  from  the  pulmonary 
arteries,  and  is  changed  to  a  bright  red  by  the  time  it 
leaves  them  to  enter  the  pulmonary  veins.  The  air  leaves 
the  lungs  warmer,  moister,  and  containing  more  carbon 
dioxid  than  when  it  entered. 

Most  of  the  mucous  membrane  lining  the  air  passages 
has  a  surface  layer  of  ciliated  cells.  Cilia  are  tiny  tlircad- 
like  projections  (Fig.  72)  which  con- 
tinually wave  to  and  fro,  the  quicker 
stroke  always  being  outward  ;  for  their 
function  is  to  remove  particles  of  dust 
and  germs  that  may  find  entrance  to 
the  air  passages.  When  the  mucus 
containing  the  dust  is  raised  nearly  to 
the  larynx,  it  may  be  thrown  out  by 
coughing.  Near  the  opening  of  the  nos- 
trils are  placed  matiy  hairs,  hundreds 
of  times  larger  than  cilia,  through  which  the  air  is  strained 
as  it  enters  the  nose.  Hairs  are  multicellular;  cilia  are 
parts  of  cells.     See  Animal  Biology,  Fig.  14. 

The  Lungs. — The  entire  chest  cavity  is  occupied  by  the 
lungs  except  the  space  occupied  by  the  heart,  the  larger 
blood  vessels,  and  the  gullet.  The  right  lung  has  three 
lobes,  or  divisions,  and  the  left  lung  has  two  lobes.  The 
lungs  are  light  pink  in  early  life,  but  become  grayish  and 
darker  as  age  advances.  This  change  is  more  marked  in 
those  who  dwell  in  cities,  or  wherever  the  atmosphere  is 
smoky  and  dusty.     The  lungs  are  covered  and  inclosed  by 


Fir,.  72.  —  Ciliated 

Cells,  lining  the  air 

passages. 


THE  RESPIRATION 


77 


a  smooth  membrane  called  the  pleura.  This  membrane 
turns  back  and  lines  the  chest  wall,  so  that  when  the  chest 
expands,  the  two  sleek  membranes  glide  over  each  other 
with  far  less  friction  than  would  be  the  case  if  the  lungs 
and  chest  wall  were  touching  (Exp.  2). 

The  Respiratory  Muscles. — (Repeat  Exps.  13,  14,  15.) 
The  chief  breathing  muscles  are  the  diaphragm  (see  Figs. 
73  and  74),  the  muscles  forming 
the  abdominal  walls  (see  Fig. 
44),  and  tivo  sets  of  short  mus- 
cles (an  internal  and  an  external 
set),  detzveeu  the  ribs.  They 
are  called  iutereostals.  (They 
are  the  flesh  eaten  when  eating 
pork  ribs.)  The  diaphragm, 
which  is  shaped  like  a  bowl 
turned  upside  down,  rounds  up 
under  the  base  of  the  lungs 
somewhat  like  a  dome  and  sepa- 
rates the  chest  from  the  ab- 
domen. Its  hollow  side  is 
toward  the  abdomen  and  its 
edges  are  attached  to  the  lowest 
ribs  and  the  vertebra  of  the 
loins.  Inspiration  is  brought 
about  by  the  rising  of  the  ribs 
and  the  descent  of  the  dia- 
phragm. Expiration  takes 
place  when  the  ribs  descend, 
the  abdominal  walls  draw  in, 
and  the  transmitted  pressure  lifts  the  relaxed  diaphragm. 

Inspiration.  —  To  cause  inspiration  the  diaphragm  con- 
tracts, it  flattens  and  descends,  since  its  edges  are  attached 


Fig.  73.  —  Vertical  Section 
OF  Trunk,  showing  dia- 
phragm, cavities  of  thorax  and 
abdomen. 


II UMAX  BIOLOGY 


lower  than  its  middle  (Fig.  Ji);  the  lungs  descend  with  it, 
thus   lengthening  the  chest  from  top  to  bottom ;  at  the 


(Esophagus 


Fig.  74.  —  Diaphragm   (or  midriff),  seen  from  below.     (Cunningham.) 

The  central  portion  (light)  is  tendinous.  As  the  diaphragm  descends,  it  acts  like  the  piston 
of  a  great  pump  and  the  blood  is  forced  up  through  the  vena  cava,  and  the  lymph  through 
the  thoracic  duct  (Fig.  66). 


same  time  the  ribs  are  raised  upward  and  outward  (Fig. 
76)  by  the  contraction  of  the  outer  set  of  muscles  between 
the  ribs.  Thus  the  cJiest  is  made  longer,  broader,  and 
deeper  from  front  to  back.  The  lungs  expand  when  the 
chest  expands,  and  the  air  rushes  in.  Why  is  this?  The 
lungs  contain  no  muscles  and  cannot  expand  themselves ; 
the  air  cannot  be  pulled  in,  for  its  parts  do  not  stick  to- 
gether.    The  true  reason  is  that  the  air  has  weight.     The 


THE  RESPIRATION 


79 


Fig.  75.  — Framework  of  Chest. 


atmosphere     has     a 

height  of  many  miles, 

and  the  air  above  is 

pressing  on  that   be- 
low.    When  the  chest 

walls  are  raised  there 

would    be    an    empty 

space  or  vacuum   be- 
tween these  walls  and 

the  lungs,  did  not  the 

pressure  of  the  outside 

air  push  air  through 

the  windpipe  into  the 

lu  11  gs     and     exp  a  n  d 

them  (Exp.  19). 

Expiration.  —  In   very  active  breathing  the  abdominal 

walls  actively  contract  so 
that  they  press  strongly 
upon  the  digestive  organs, 
which  in  turn  press  the 
diaphragm  up.  The  ribs 
are  also  drawn  dozen  and 
in.  Thus  the  chest  be- 
comes smaller  and  forces 
the  air  to  flow  out  through 
the  windpipe  (Exps.  20 
and  21). 

Thought  Questions.  —  Why 
breathing  with  the  waist  is  easier 
than  breathing  with  the  upper 
chest.      Effects  of  confining  the 

EIg.   76.  — Blackboard    Sketch,    to      waist. 

show  how  the  chest  is  expanded  when  I .   There  are  two  pairs  ot  

the  ribs  move  upward  and  outward.  ribs  below,  while  there  are  none 


So 


HUMAN  BIOLOGY 


above.     2.  There  are  three  pairs  of ribs  below,  while  there  are 

none  above,  but   all    ribs  of  the  upper  chest  are ribs.      3.    The 

lower  of  the  joints  between  the  seven  pairs  of  true  ribs  and  the  sternum 

are  more  flexible  than  the  upper  joints  because  .     (Observe  the 

joints  in  Fig.  75.)     4.    The  walls  of  the  waist   swing and , 

while  the  walls  of  the  upper  chest  must  move and  .     5.  The 

bones  of  the rest  upon  the  upper  chest.      In  upper  chest  breathing 

their  weight,  and  the  weight  of  both  of  the must,  therefore,  be 

lifted.     (Fig.  28.)     Test  by  trying  it. 

Hygienic   Habits  of   Breathing.  —  Chest  breathing  uses 
chest  chiefly,  abdominal  breathing  uses  abdomen  chiefly, 


Fig.  77.  Fig.  78.  Fig.  79. 

Fig.  77.  —  Female  Figure  encased  in  Corset.  Expansion  at  the  waist  is  here  impossi- 
ble and  the  breathing  is  called  "  collar-bone  breathing." 

Fig.  78.  —  Male  Figure.  Here,  owing  to  pressure  of  clothing  and  faulty  position,  expan- 
sion of  chest  is  hindered  and  breath  is  taken  by  the  "  abdominal  method." 

Fig.  79.  —  Figure  Properly  Poised  and  Free.  Here  the  entire  thorax  can  move  freely, 
and  natural  breathing  is  the  result.     (For  blackboard.)     From  Latson. 

full  breathing  uses  both.  These  three  forms  depend 
upon  whether  the  breathing  is  carried  on  by  using 
the  muscles  of  (1)  the  chest,  (2)  the  abdomen,  or  (3)  both 
(see  Figs.  77,  78,  79).  There  has  been  much  debate 
among  physicians,  surgeons,  and  singers  as  to  which  of 
these  methods  is  best.  Probably  this  question  would  not 
have  been  raised  but  for  the  confining  and  deforming 
effect  of  clothing  upon  the  waist.      Full  breathing  is  used 


THE  RESPIRATION  8 1 

by  children  of  all  races,  by  both  men  and  women  of  wild 
tribes,  and  by  men  of  civilized  countries.  It  is  undoubtedly 
the  natural  way,  as  well  as  the  easiest  and  most  effective 
way  (Exps.  16,  17,  18). 

Breathing  with  the  upper  chest  is  exhausting  because  of  the  stiffness 
of  the  upper  part  of  the  bony  cage  (see  Fig.  75) ;  for  it  is  inclosed  by 
true  ribs  fixed  to  the  breastbone  by  short  cartilages.  The  ribs  in  the 
waist  (Fig.  75)  are  either  floating  in  front  or  fixed  by  long  cartilages  to 
the  ribs  above.  In  pure  abdominal  breathing  the  diaphragm  must  con- 
tract more  than  in  full  breathing  in  order  to  descend,  because  its  edges 
have  been  drawn  together  and  fixed  by  binding  the  ribs  at  the  waist. 
In  full  breathing  the  floating  and  false  ribs  at  the  waist  (five  pairs  in 
all)  float  in  and  out  as  nature  provided.  As  they  move  out,  this 
broadens  and  deepens  the  chest,  and  aids  the  flattening  of  the  dia- 
phragm by  moving  its  edges  farther  apart.  Those  persons,  perhaps 
one  in  a  thousand,  who  voluntarily  deform  the  body  with  tight  clothing 
are  beneath  contempt.  But  so  uniform  is  the  pressure  of  tight  clothes 
and  shoes  that  the  wearer  soon  becomes  unconscious  of  them,  and  so 
powerful  are  the  effects  that  not  one  person  in  a  thousand  escapes 
deformity  and  injury.  Children's  clothing  should  be  supported  by  the 
shoulders,  and  adults'  clothing  by  both  shoulders  and  hips,  but  by 
the  waist,  never. 

Cellular  Respiration.  —  The  chemical  activities  within  the  cells  and 
their  need  of  oxygen,  not  the  amount  of  oxygen  in  the  lungs  or  blood, 
determine  how  much  oxygen  the  cells  absorb  from  the  blood.  Oxygen 
cannot  be  forced  even  into  the  blood  beyond  the  required  amount. 
Deep  breathing  movements,  however,  help  the  flow  of  the  blood  and 
lymph.     Carried  to  excess,  they  tire  the  will  and  exhaust  the  nerves. 

Changes  in  Blood  while  in  the  Lungs.  —  The  coloring 
matter  (or  hemoglobin)  of  the  corpuscles  absorbs  oxygen 
(and  becomes  oxy-hemoglobin).  Carbon  dioxid  is  given  off 
from  the  plasma.     The  blood  becomes  a  brighter  red. 

Changes  in  Air  in  the  Lungs.  —  The  air  entering  the 
lungs  consists  of  about  one  fifth  oxygen  and  four  fifths 
nitrogen.  This  nitrogen  is  of  no  use  to  the  body,  and  is 
exhaled  unchanged.  A  part  of  the  oxygen  inspired  is  taken 
up  by  the  blood,  and  carbon  dioxid  is  sent  out  in  its  place. 


82 


I/CMAX  BIOLOGY 


About  half  a  pint  of  water  is  given  off  through  the  lungs 
in  a  day.  Minute  quantities  of  injurious  animal  matter 
are  also  given  off  in  the  breath  from  even  the  soundest 
person.  The  air  leaves  the  lungs  warmer,  damper,  and  with 
more  carbon  dioxid  than  when  it  entered  (Exps.  3  to  9). 

Persons  with  decayed  teeth,  catarrh,  indigestion,  diseased  lungs,  or 
other  unsoundness  give  off  still  more  of  this  material.  When  many 
people  are  assembled  in  a  badly  ventilated  room,  the  amount  of  injurious 
animal  matter  in  the  air  is  much  increased,  and  is  called  "  crowd  poison" 
Its  odor  is  strong  and  repulsive  to  one  who  just  enters  the  room,  but 
the  sense  of  smell  becomes  dull  to  it  in  a  few  minutes.  It  would  seem 
that  nature  gives  a  fair  warning  against  harm;  but  if  we  disregard  the 
warning  it  soon  ceases. 

People  who  are  really  Unclean.  —  Nature's  plan  seems  to  be  for  us  to 
live  out  of  doors.  Air  once  breathed  is  impure.  It  is  just  as  unfit  to 
enter  our  bodies  as  muddy  water  or  decayed  food.     Yet  many  who  call 

themselves  cleanlv 
and  refined,  and 
will  not  allow  a 
speck  of  dirt  to 
remain  on  their 
clothes,  nor  use  a 
spoon  just  used  by 


W&L 


\ 


V 


ffffffffff^h 


another,     do     not 

object  to  breathing 

t-  c  ^  into    their    lungs, 

Fig.  80.  —  Ventilation  of  Stove-heated  Room.1  *  ' 

over   and  over 

How  are  the  inlet  and  outlet  situated  with  reference  to  the  stove  ?  .  .  _ 

again,  the  cast-off 
air  from  the  lungs  of  ot Iters.  If  a  window  is  opened  for  ventilation, 
they  are  horror-stricken  for  fear  of  drafts.  Drafts  are  injurious  only  to 
persons  perspiring,  or  to  those  who  have  coddled  the  skin  by  continu- 
ally overheating  it.  There  are  thousands  of  schools,  churches,  and 
theaters  all  over  the  land  which  reek  dailv  with  the  malodorous  particles 
from  the  lungs  of  their  occupants.  Although  the  air  in  them  is  odorless 
to  those  who  occupy  them,  it  is  disgusting  to  any  one  who  enters  from 
the  fresh  air.  Figure  80  shows  the  correct  ventilation  of  a  stove-heated 
schoolroom. 

Dust  causes  catarrh  of  the  bronchial  tubes  and  chronic 

From  Coleman's  Elements  of  Physiology  (400  pp.).   The  Macmillan  Co.,  N.Y.      * 


THE  RESPIRATION  83 

inflammation  of  the  lungs  ;  it  prepares  for  consumption, 
by  gradually  weakening  the  lungs  of  those  who  breathe 
it.  Intelligence  and  common  sense  are  necessary  to  pre- 
vent it  from  accumulating  in  the  house.  The  chief  pur- 
pose of  the  house  cleaning  should  be  not  only  to  remove 
bits  of  paper  from  the  floor,  which  do  no  harm  even  to  the 
shoes,  but  to  remove  impurities  from  the  air.  It  does  no 
good  to  stir  up  the  dust  .and  allow  it  to  settle  down  again 
(Exp.  12).  In  many  houses  dust  is  thus  allowed  to 
accumulate  for  months.  Experiments  show  that  dust  and 
germs  floating  in  the  air  are  not  diminished  to  a  great  extent 
by  a  gentle  draft  through  the  room.  The  windows  must 
be  open  and  sweeping  done  in  the  direction  of  the  air 
currents  ;  the  windows  should  be  left  open  for  a  long  while 
after  the  sweeping.     A  windy  day  is  best  for  sweeping. 

The  habit  some  housekeepers  have  of  buying  furnishings  and  bric- 
a-brac  for  the  home  until  it  looks  like  a  retail  store  or  junk  shop,  makes 
it  almost  impossible  to  clean  their  houses.  A  few  articles,  carefully 
selected,  adorn  a  home  more  than  many  bought  at  random,  and  they  do 
not  litter  the  house  and  serve  as  traps  for  dust.  With  all  precautions 
some  dust  may  settle  down.  This  should  not  simply  be  stirred  up  again 
with  a  feather  duster,  but  the  dusting  should  be  dune  with  a  damp  cloth. 
Ashes  should  be  sprinkled  before  they  are  moved.  Carpet  sweepers, 
but  never  brooms,  should  be  used  upon  carpets.  Carpets  and  lace  cur- 
tains are  truly  dust  traps,  in  which  dust  will  accumulate  without  limit. 
Those  who  value  the  health  will  not  use  such  uncleanly  abominations, 
at  least  in  bedrooms.  Though  linoleum,  bare  floors  with  movable  rugs, 
oiled  and  painted  floors,  may  not  look  so  comfortable  as  a  fixed  carpet, 
they  bring  far  more  comfort  in  the  end.  The  weakening  effect  of  ordi- 
nary dust  is  one  of  the  chief  causes  of lung  diseases,  and  prepares  a  fertile 
soil  for  the  consumptive  germ.  The  sputum  coughed  up  by  consump- 
tives falls  upon  the  floor  or  street,  soon  dries,  and  the  germs  are  driven 
about  by  the  wind.  In  many  cities  there  is  a  law  against  spitting  in 
public  places,  and  the  streets  are  flushed  with  water  before  they  are 
swept. 

Ventilation  presents  no  difficulties  in  the  summer  time 

or   in    warm  climates.     The  reason  that  it  is   a  difficult 


84 


HUMAN  BIOLOGY 


question  in  cold  weather  is  because  the  air  furnished  must 

be  not  only  pure,  but  warm.     To  keep  cold  air  out  often 

means  to  keep  foul  air  in.     Heating  with  hot  air,  by  which 

system  pure  air  is  passed  over 
a  furnace,  and  fresh  air  con- 
stantly  admitted,  may  be  a  good 
method  (Figs.  80,  81),  but  is 
often  a  dismal  failure  because 
it  dries  out  the  air,  which  in 
turn  dries  out  the  skin.  To 
prevent  this,  wide  vessels  of 
water  should  be  set  at  the  in- 
lets. Dry  air  is  cooling.  Why  ? 
Dr.  Barnes  proved  that  moist 
air  at  650  is  as  comfortable  as 
dry  air  at  710.  Air  saturated 
with  vapor  at  6o°  will  only  be 
50  per  cent  saturated  at  8o°. 
Such  air  dries  out  the  mucous 
membrane    of    eyes,    nose,   and 

throat.     Heating  by  hot  water  circulating  in  pipes,  or  by 

steam,    gives    no    means    of 

introducing    fresh    air,    and 

is     likely    to    cause    worse 

ventilation    than    any  other 

method.      The     radiators 

should  stand  close  to  win- 
dows or  other  fresh-air  inlet, 

that  the  air  may  be  heated 

as  it  enters,  and  the  outlet 

for   air   should   be    farthest 

from  the  radiators.     The  same  rules  apply  to  heating  by 

stoves.      An    oil    stove    for    heating    is    an    inconceivable 


FIG.  81.  —  The  air  enters  through 
a  special  inlet  and  is  warmed 
as  it  passes  through  hood  sur- 
rounding the  stove. 


a- 


FIG.  82.  —  Chimney  with  a  passage  be- 
hind fireplace,  or  grate,  in  which  the 
air  is  warmed  as  it  enters. 


THE   RESPIRATION 


85 


iniquity  to  any  but  a  person  densely  ignorant  of  hygiene. 
Heating  by  fireplaces  (Fig.  82)  is  the  most  healthful  of 
all  methods,  for  there  is  a  constant  removal  of  air  through 
the  chimney,  and  this  air  will  be  replaced ;  even  if  all 
doors  and  windows  are  closed,  it  will  come  in  through  tiny 
cracks.  Radiant  heat  travels  in  straight  lines  from  a 
fireplace  and  warms  solid  objects,  but  not  the  air  passed 
through.  Hence  an  open  fire  will  keep  the  body  warm 
with  the  room  at  a  low  temperature.  Fireplaces,  however, 
do  not  afford  sufficient  heat  in  severe  climates. 

Stoves  are  not  as  healthful  as  fireplaces,  for  there  is  not 
so  much  air  removed  through 
the  pipe  as  through  the 
chimney.  Carbon  monoxid, 
unlike  carbon  dioxid,  is  an  ac- 
tive poison  causing  the  blood 
corpuscles  to  shrivel.  It 
passes  through  red-hot  iron 
or  a  cracked  stove  or  furnace. 


Fig.  83. —  Blackboard  Sketch. 


Reasons  for  Breathing  through  the 
Nose  (Fig.  83). —  (1)  The  many 
blood  vessels  in  the  mucuous  mem- 
brane lining  the  nasal  passages  so 
heat  the  air  that  it  does  not  irritate  the  bronchial  tubes.     (2)  The  hairs 

in  the  nostrils  strain  the  air  and  catch 
dust ;  the  cilia  of  the  nasal  passages 
also  do  this.  (3)  A  mouth-breather 
often  swallows  food  before  chewing  it 
sufficiently,  because  he  cannot  hold  his 
breath  longer.  (4)  The  nasal  mucous 
membrane  of  an  habitual  mouth- 
breather  dries  and  shrinks  and  ob- 
structs the  circulation,  bringing  on 
catarrh  of  the  nose.  (5)  Mouth  breath- 
ing causes  an  unpleasant  expression  of 
countenance    (see   Fig.  84).     (6)    The 


Fig.  84.  —  Facial  expression  in 
mouth  breathing,  and  breath- 
ing through  the  nose. 


86  HUMAN  BIOLOG\ 

breath  does  not  come  through  the  nose  as  quickly  as  through  the 
mouth ;  the  lungs  are  kept  more  expanded,  and  one  does  not  get 
"out  of  breath"  so  quickly.  (7)  The  voice  of  the  month  breather  has 
a  hard  twang,  not  a  full,  resonant  tone  as  when  the  nostrils  are  open. 
(8)  Flavors  and  odors  are  better  appreciated.  Sometimes  the  sense 
of  smell  is  almost  lost  by  mouth  breathers.  If  one  cannot  breathe 
through  the  nose,  even  for  a  short  time,  there  is  probably  an  adenoid, 
or  tonsil-like,  growth  in  nose  or  pharynx,  and  a  physician  should  be 
consulted.     '"Adenoids"  are  glandular  or  grapelike  in  form. 

Diseases  of  the  Respiratory  Organs.  —  A  cold  or  catarrh  is  an  inflam- 
mation of  a  mucous  membrane.  If  the  inflammation  is  in  the  nasal  pas- 
sages, it  is  called  a  cold  in  the  head  ;  if  it  is  in  the  pharynx,  it  is  called 
a  sore  throat ;  if  it  is  in  the  larynx  or  voice  box,  there  is  hoarseness; 
if  it  is  in  the  bronchial  tubes,  it  is  bronchitis ;  finally,  if  it  is  in  the  air 
cells,  it  is  pneumonia.  If  the  air  is  cut  off  from  access  to  the  air  cells, 
there  is  an  attack  of  the  painful  disease  called  asthma,  which  is  accom- 
panied by  a  feeling  of  suffocation.  Some  believe  that  asthma  is  caused 
by  the  mucous  membrane  lining  the  finest  bronchial  tubes  becoming 
inflamed  and  swollen,  and  closing  the  tubes ;  others  think  that  the 
muscles  in  the  large  bronchial  tubes  contract  and  close  the  tubes. 
Pleurisy  is  inflammation  of  the  pleura  and  makes  breathing  painful. 
If  much  fluid  forms  between  the  pleuras,  the  inner  pleura  may  press 
upon  the  lungs  and  interfere  with  breathing.    . 

Alcohol  not  only  weakens  the  blood  vessels  near  the  sur- 
face, but  the  blood  vessels  in  general.  Weakened  and 
congested  blood  vessels  in  the  lungs  make  them  more 
liable  to  pneumonia  and  other  congestive  diseases.  Con- 
tinual congestion  causes  an  abnormal  growth  of  connec- 
tive tissue  fiber  in  the  walls  of  the  cells.  This  diminishes 
the  capacity  of  the  lungs  and  interferes  with  the  exchange 
of  carbon  dioxid  and  oxygen. 

Tobacco.  —  It  is  often  asked  why  cigarettes  are  so  much 
more  injurious  to  the  health  than  pipes  and  cigars.  The 
nature  of  the  paper  of  cigarettes  and  various  other  absurd 
reasons  have  been  assigned.  The  true  reason  is  that  the 
cigarette  smoker  usually  inhales  the  tobacco  smoke.  Cigar 
smoke,  if  drawn  into  the  lungs,  would  usually  be  coughed 
up  at  once.      Cigarette  smoke  is  weaker  —  it  is  so  weak 


THE  RESPIRATTOX 


87 


that  the  smoker  is  not  content  simply  to  absorb  the  nicotine 
through  the  mucous  membrane  of  the  mouth  ;  he  draws  it 
into  the  lungs.  The  very  mildness  of  the  smoke  leads  to 
inhalation.  Hence,  as  the  surface  of  the  lungs  is  a  hundred 
times  greater  than  the  surface  of  the  mouth,  and  its  lining 
m itch  thinner,  cigarette  smoking  is  far  more  injurious  than 
cigar  smoking. 

The  poison  accumulates  in  the  bowl  of  a  pipe ;  hence  an  old  pipe 
is  very  injurious.  The  irritation  of  tobacco  smoke  often  sets  up  a 
chronic  dry  catarrh 
of  the  air  passages  ; 
rarely  it  causes  cancer 
of  lips  or  tongue.  Sir 
Henry  Thompson 
says  :  "  The  only  per- 
sons who  enjoy  smok- 
ing and  find  it  tran- 
quillizing at  times  are 
those  who  smoke  in 
great  moderation. 
Men  who  are  rarely 
seen  without  a  cigar 
between  t4ie  lips,  have 
long  ceased  to  enjoy 
smoking.  They  are 
confirmed  in  a  habit, 
and  are  merely  miser- 
able when  the  cigar  is 
absent.1'  They  do  not 
smoke  for  pleasure, 
but  to  escape  misery 
which  wiser  men 
escape  by  avoiding 
tobacco  altogether. 


Fig.  85.  Fig. 

Fig.  85.  —  Flattened  Chest  and  waist  organs 
sunken  from  wearing  tight  clothing  since  the  age  of 
fourteen.  Such  women  often  walk  with  bodies 
bent  forward  to  hide  the  prominent  abdomen. 

Fig.  86.  —  A  Natural  Woman. 


Practical  Ques- 
tions.— 1.    State 

how  in  the  case  of  a  person  with  round  shoulders  a  gradual  remolding 
of  cartilages  (which  ones  ?),  the  strengthening  of  the  muscles  (which 
ones  ?),  and  the  practice  of  deep  breathing  may  each  contribute  toward 


ss 


II  CM  AN  BIOLOGY 


acquiring  an  ei^ct  and  perfect  figure.  2.  Should  a  hat  be  well  venti- 
lated? (A  punch  tor  making  the  holes  costs  a  dime.)  Should  a  hat 
be  stiff  or  soft  ?  3.  Name  habits  that  im- 
pair the  power  qif  the  lungs.  4.  How  could 
you  convince  a  person  that  a  bedroom 
should  be  open  while  and  after  it  is  swept  ? 
That  it  should  be  ventilated  at  night  ? 
5.  Which  is  the  more  injurious  to  others, 
tobacco  chewing  which  causes  the  ground 
to  be  unclean,  or  smoking  which  renders 
the  air  impure  ?  6.  Why  do  those  who 
stand  straight  up  to  hoe  not  get  tired  half 
so  quickly  as  those  who  bend  or  "hump1' 
over?  (Chap.  VI.)  7.  Why  do  students 
who  sit  in  rocking  chairs,  or  from  other 
causes  lean  the  head  forward  when  they 
study,  often  find  that  they  recover  from 
drowsiness  if  they  sit  erect,  or  sit  in  a 
straight  chair?  8.  How  are  high  collars 
a  fruitful  source  of  bad  colds  ?  9.  If  the 
draft  up  the  chimney  of  the  fireplace,  when 
the  fire  is  burning,  takes  up  a  volume  of  air  sufficient  for  many  people, 
why  is  it  unnecessary  to  open  a  window?  10.  Why  does  cold  impure 
air  make  a  person  colder  than  cold  pure  air?  (p.  14.)  11.  Do  the 
modern  customs  of  uniformity  in  dress  for  all  classes  and  climates, 
shipping  foods  from  great  distances,  one  section  or  nation  imitating  the 
ways  of  another  section  or  nation,  lead  toward  health  or  disease?  Do 
such  customs  violate  or  conform  to  the  great  biological  law  that  life  is 
a  process  of  adaptation  to  environment? 


Fig.  87.  —  Suspenders 
should  have  a  pulley  or 
lever  at  the  back,  that  the 
strap  on  one  side  may 
loosen  when  one  shoulder 
is  raised. 


Colored  Figure  6.  —  Organs  of  the  Trunk. 

c/>,  collar  bone;  r,  ribs;  z,  tongue  bone  (hyoid) ;  k,  k,  cartilages  of  larynx;  /,  windpipe; 
j,  thyroid  gland;  >-',  right  ventricle;  Iv,  left  ventricle;  ru,  right  auricle;  hi,  left  auricle; 
a,  aorta;  ka,  artery  to  head  (carotid);  sa,  subclavian  artery;  la,  pulmonary  artery; 
ok,  superior  vena  cava;  hv,  jugular  vein;  lu,  lungs;  f,  diaphragm;  lb,  liver;  g,  gall 
bladder;  s,  stomach;  x,  spleen;  «.  mesentery  with  vessels;  d,  small  intestine;  gd,  large 
intestine;   b,  caicum;   w,  vermiform  appendix;   //.bladder. 


CHAPTER   VII 
FOOD   AND   DIGESTION 

Experiment  i.  Tests  for  Acid,  Alkaline,  and  Neutral  Substances.  — 
Repeat  tests  described  in  General  Introduction.1 

Experiment  2.    Test  for  Starch.  — See  General  Introduction. 

Experiment  3.    Test  for  Grape  Sugar.  —  See  General  Introduction. 

Experiment  4.    Test  for  Proteid.  —  See  General  Introduction. 

Experiment  5.    Test  for  Fats.  —  See  General  Introduction. 

Experiment  6.  Human  Teeth.  —  Study  the  form  of  teeth  from  every 
part  of  the  mouth.  Get  a  handful  from  a  dentist.  Break  some  of  the 
teeth  to  make  out  their  structure.  Classify  them.  Draw  section, 
enlarged. 

Experiment  7.  Study  of  the  Teeth.  (At  home.)  —  Sit  with  the  back 
to  the  light  and  look  into  a  mirror,  with  the  mouth  wide  open.  Do  you 
see  the  four  kinds  of  teeth  named  in  text  ?  Which  are  fitted  for  cut- 
ting ?  Which  for  grinding?  Are  any  suited  for  tearing?  Are  any  of 
the  teeth  pointed?  What  is  the  difference  in  the  bicuspids  and  molars? 
Are  there  any  decayed  places?  Are  the  teeth  clean?  Are  the  so-called 
canine  teeth  so  long  that  they  project  beyond  the  line  of  the  other  teeth, 
as  they  do  in  a  dog?  Do  the  edges  of  the  upper  and  lower  incisors 
meet  when  the  mouth  is  closed,  or  do  they  miss  each  other  like  the 
blades  of  scissors?  How  many  roots  has  each  lower  tooth?  (See  Fig. 
92.)     Which  tooth  has  the  longest  root? 

Experiment  8.  Structure  of  Mammalian  Stomach.  —  Get  a  piece  of 
tripe  from  the  market.  Study  its  several  coats.  The  velvety  inner 
coat  is  covered  with  mucous  membrane.      (Photomicrograph,  Fig.  95.) 

Experiment  9.  Model  of  Human  Food  Tube.  — Make  a  model  of  the 
food  tube  out  of  yellow  cambric,  giving  to  each  organ  its  correct  size. 
Follow  the  dimensions  given  in  text. 

Necessity  for  Foods.  —  Growing  plants  and  growing  ani- 
mals need  new  material  to  enable  them  to  increase  in  size 
or  grow.  Plants  never  cease  to  grow  while  they  live; 
most  mammals  attain  their  full  size  in  one  fifth  of  the  time 

1  See  also  Peabody's  "  Laboratory  Exercises  in  Physiology,"  Holt,  N.Y. 

89 


90  HUMAN  BIOLOGY 

occupied  by  their  whole  lives.  (By  this  rule  how  long 
ought  man  to  live?)  Animals,  moreover,  move  from  place 
to  place,  and  work  with  their  muscles.  The  energy  for  this 
comes  from  the  food  they  eat.  Plants  do  not  use  food  for 
this  purpose.  Another  need  for  food  comes  from  the 
necessity  for  heat  in  all  living  things.  The  activities  of 
animals  cause  the  tissues  to  wear  out,  or  break  down,  and 
food  furnishes  material  with  which  new  living  matter  is 
built  up  by  the  cells  and  the  tissues  repaired.  We  have 
already  stated  the  role  of  oxygen  in  setting  free  energy  in 
the  living  substance  of  the  cell  by  oxidizing  it.  There  is 
no  furnace  in  the  body  as  in  an  engine,  but  the  oxidation 
occurs  in  the  cells  themselves  and  the  fuel  is  built  up  into 
living  matter  by  the  cells  before  it  is  oxidized.  Plants 
must  lift  mineral  from  the  inorganic  to  the  organic  world 
before  it  can  be  food  for  animals.  Plants  can  assimilate 
minerals  ;  animals  cannot.  The  body  cannot  make  bone 
out  of  limewater.  The  iron  in  iron  tonics  cannot  be  used. 
Iron  makes  the  grain  brown,  and  the  peach  red.  There 
is  ten  times  as  much  iron  in  our  food  as  the  body  needs. 

State  four  reasons  why  animals  need  food.  Which  of 
these  reasons  is  very  powerful  with  plants  ?  Least  powerful? 
Absent  altogether  ?  Why  is  constant  breathing  necessary 
for  life  ?  When  is  breathing  more  rapid  ?  Why?  People 
who  lead  what  kind  of  lives  usually  have  poor  appetites  ? 
Good  appetites  ?  Why  ?  What  was  the  first  distinct  or- 
gan evolved  by  animals  ?     (Animal  Biology,  Chap.  IV.) 

The  Body  is  a  Machine  for  transferring  Energy.  —  Energy 
cannot  be  destroyed,  but  it  can  be  transferred  and  changed 
in  form.  When  a  coin  is  rubbed  on  the  table,  muscular 
energy,  supplied  by  oxidation  in  the  muscle,  produces  the 
motion.  Friction  may  change  motion  into  heat,  and  the 
coin   will   become   very    hot.     The    uniting   of    food   and 


FOOD  AND  DIGESTION  91 

oxygen  in  the  cells  of  the  body  gives  the  heat  and  motion 
(energy)  of  the  body.  Only  substances  which  will  oxidize, 
or  burn,  are  true  foods.  Water,  salt,  and  carbon  dioxid 
will  not  burn;  hence,  they  cannot  give  rise  to  energy  in 
the  body.  But  the  sun  energy,  acting  in  the  green  leaf, 
tears  apart  the  carbon  from  the  oxygen  (Plant  Biology, 
Chap.  XIII),  sets  free  the  oxygen,  and  the  carbon  is  stored 
in  starch  for  future  burning.  Sunshine  is  energy  (light 
and  heat).  The  sun  sustains  the  life  of  plants  and  through 
them  the  life  of  animals.  The  oxidation  in  the  body  is  so 
slow  that  it  can  hardly  be  called  a  burning,  but  it  is  faster 
than  the  oxidation  of  iron  in  rusting  or  of  wood  in  rotting, 
and  is  about  equal  to  the  continual  burning  of  two  candles. 
The  Four  Kinds  of  Nutrients,  or  Food  Stuffs.  —  The  kinds 
of  food  which  we  eat  seem  to  be  numberless,  but  they  con- 
tain only  four  kinds  of  food  stuffs,  —  starches,  fats,  proteids, 
and  minerals.  Many  foods  contain  all  four  classes  of 
food  stuffs.  Milk  contains  sugar  (a  changed  form  of 
starch),  cream  (a  fat),  curd  (a  proteid),  and  water  (a  min- 
eral).    Oatmeal  contains  starch,  oil,  gluten,  and  water. 

Uses  of  the  Nutrients,  or  Food  Stuffs 

1.  Proteids.     The  tissue-building  foods  (also  of  value  as  fuel). 

2.  Starches  (and  sugars)   1  Energy  and  heat  (fuel)  and 

3.  Fats  (and  oils)  J       fat  producing  foods. 

4.  Minerals  (water,  salt).     Important  aids  in  using  other  foods. 

Relative  Fuel  Value.  —  A  pound  of  fat  produces  as  much 
heat  in  the  body  as  2.3  lb.  of  proteid  or  2.3  lb.  of  starch, 
the  last  two  having  equal  fuel  value  in  the  body. 

Starch  and  the  sugars  are  closely  related;  starch  readily 
changes  into  sugar.  They  contain  much  carbon  and  are 
called  carbohydrates.  Starch  is  especially  abundant  in 
grains,  seeds,  and  fleshy  roots  (Fig.  88).  The  sugar  in 
ripe  fruit  and  in  honey  is  called  fruit  sugar.     Milk  sugar 


92 


HUMAN  BIOLOGY 


is  found  in  sweet  milk.      Crape  sugar  is  found  in  grapes 
and  honey ;  the  small  grains    seen   in    raisins    consist    of 

grape  sugar ;  it  can  also 
be  prepared  artificially 
from  starch.  Cane  sugar 
is  found  in  cane,  in  sap 
of  the  maple,  and  in  the 
sugar  beet  (Exps.  2,  3). 
Fats  include  the  fats 
and  oils  found  in  milk, 
flesh,  and  plants.  A 
fat,  such  as  tallow,  is 
solid  at  the  ordinary 
temperature ;  while  an 
oil,  such  as  olive  oil,  is 
liquid  at  the  same  tem- 
perature. Tallow  was 
oil  while  it  was  in  the 
warm  body  of  the  ox.  Sugar  is  transformed  into  fatty 
tissue  as  readily  as  is  fatty  food  itself. 

Proteids  are  the  only  foods  that  contain  the  tissue- 
building  nitrogen.  Protoplasm  cannot  be  formed  without 
nitrogen.  We  do  not  often  see  a  pure  proteid  food,  for 
this  food  stuff  is  not  so  readily  separated  from  foods 
containing  it  as  are  starch,  sugar,  and  fat.  AWmmeu, 
or  white-of-egg,  is  proteid  united  with  four  times  its 
weight  of  water.  Pure  proteid  is  also  called  albumin. 
Coagulation  by  heat  is  one  test  for  proteid  (Exp.  4). 
These  are  the  names  of  proteids,  or  albumins,  found  in 
several  common  foods :  casein,  the  curd  or  cheesy  part  of 
milk ;  myosin  of  lean  meat ;  Jibriji  in  blood  ;  legumin 
in  beans  and  peas  ;  gluten,  or  the  sticky  part  of  wet  flour ; 
gelatin  in  bones.     Proteid  is  valuable  to  the  body  as  fuel 


Fig.  88.  — A  Tiny  Bit  of  Potato,  highly 
magnified,  showing  cells  filled  with  grains 
of  starch.    Cooking  bursts  these  cells. 


FOOD   AND   DIGESTION  93 

as  well  as  a  tissue  builder.  We  could  burn  beans  and 
peas  as  well  as  the  strictly  fuel  foods,  starch  and  fat,  in 
an  engine,  and  get  heat  to  move  the  engine.  If  one  takes 
up  athletics  or  hard  physical  labor,  he  should  increase  the 
amount  of  fats  and  carbohydrates  eaten,  but  not  of  proteid. 
Muscular  activity  increases  the  carbon  waste  but  not  the 
nitrogen  waste  of  the  body. 

Minerals.  —  The  iron  of  the  blood  and  the  mineral  salts 
in  bone  (carbonate  and  phosphate  of  lime)  must  enter  the 
body  in  organic  form  in  order  to  be  used.  Water  and  salt 
are  mineral  foods.  The  body  is  about  two  thirds  water. 
The  cells  must  do  their  work  under  water.  They  cannot 
live  when  dried.  Water  enables  the  blood  to  flow ;  and 
the  blood  is  not  only  the  feeder,  but  also  the  washer  and 
cleanser  of  the  tissues.  Some  persons  get  out  of  the  habit 
of  drinking  plenty  of  water,  and  their  health  suffers  thereby. 
In  such  a  case  drinking  plenty  of  water  will  be  safer  and 
more  effective  than  taking  poisonous  drugs  to  restore  health. 

Adulteration  of  Food.  —  Sometimes  cheaper  materials,  of 
little  or  no  value  as  food  but  of  no  great  injury  to  health, 
are  added  to  foods.  Examples:  water  added  to  milk, 
sawdust  to  ground  spices,  chicory  to  coffee,  glucose  to 
maple  syrup.  Other  f,orms  of  adulteration  not  only  cheat 
the  purse  but  tend  to  destroy  health,  or  actually  do  so. 
Examples:  Boracic  acid  or  formalin  added  to  milk  to 
prevent  souring,  copper  to  canned  peas,  etc.,  to  give  a 
bright  green  color  ;  salicylic  acid  or  borax  used  in  minute 
quantities  as  a  preservative  with  canned  corn,  tomatoes, 
etc.;  acids  added  to  "apple"  vinegar;  dried  fruit  treated 
with  sulphur  to  prevent  a  dull  color.  Pure  food  laws  tend 
to  repress  these  evils.  It  is  best  to  buy  foods  in  their 
original  form.  For  instance,  lemons  are  more  reliable 
than   vinegar.     A  bit  of  lemon   at  each  plate,  in    house- 


94  HUMAN  BIOLOGY 

holds  that  can  afford  it,  is  far  preferable  to  vinegar.  We 
should  always  buy  from  neighbors  when  possible.  Farmers 
and  gardeners  should  do  their  own  drying  and  canning. 
For  purity  of  water,  see  Chap.  X. 

The  Daily  Ration.  —  A  quarter  of  a  pound  (4  oz.)  of  pro - 
teid  foods  and  one  pound (  16  oz.)  of  fuel  foods  (total  20  oz. 
of  water-free  foods)  are  needed  to  replace  the  daily  waste 
of  the  body.  Hence  a  balanced  ration  has  proteid  and  fuel 
food  in  the  ratio  of  4  to  16,  or  1  to  4.  But  recent  experi- 
ments at  Yale  University  indicate  that  2  oz.  of  proteid 
daily  are  more  strengthening  than  four. 

Appetite  is  a  perfect  guide  for  those  who  lead  an  active 
life  and  eat  slotvly  of  simple  food.  Highly  seasoned  food 
and  complex  mixtures  deprave  the  appetite ;  it  then  leads 
astray,  instead  of  guiding  safely.  Of  course  the  appetite 
cannot  guide  one  to  eat  the  right  kind  and  quantity  of 
food  at  a  table  where  the  food  lacks  any  of  the  four  neces- 
sary food  stuffs,  or  where  innutritious  or  indigestible  food 
is  provided.  It  is  well  to  select  one  food  for  a  meal  be- 
cause it  is  rich  in  proteids,  another  because  it  is  rich  in  fat, 
and  the  third  because  it  is  rich  in  starch  or  sugar.  (See 
table,  p.  95.)  Intelligence  in  regard  to  diet  enables  a 
housekeeper  to  provide  nourishing  food  for  less  money 
than  an  ignorant  housekeeper  often  pays  for  food  deficient 
in  nourishing  qualities. 

A  Balanced  Ration.  —  A  deficiency  of  starch  may  be 
supplied  by  an  excess  of  fat  or  sugar.  It  is  most  essential 
to  provide  proteid  as  it  cannot  be  replaced  by  any  other 
food  stuff.  An  excess  of  proteid  is  most  harmful.  An  ex- 
cess of  starch  or  fat  is  oxidized  into  water  and  carbon 
dioxid,  which  are  harmless  waste  products  ;  an  excess  of 
proteid  is  changed  into  urea  which  may  become  harmful 
by  overworking  the  liver  and  kidneys  which  excrete  it. 


FOOD  AXD  DIGESTION 


95 


Composition  of  One  Ounce  of  Various  Foods  in  Fractions  of 

an  Ounce 


Daily  Ration 

I.   Nuts. 

Pecan    .     .     . 
Walnut       .     . 
Almonds    .     . 
Cocoanut   . 
Chestnut     . 

II.   Fruits. 

Peach    . 


Apple    . 
Blackberry 
Cherry  . 
Grape    . 
Fig  (dried ) 
Banana 


III.   Animal  Food. 
Lean  beef 
Fat  pork    .     . 
Smoked  ham 
Whitefish  .     . 
Poultry       .      . 
Oysters       .     . 
Cow's  milk 
Eggs      .     .     . 
Cheese 
Butter   .     .     . 


IV. 


Pods  or  Legumes. 
Beans  .... 
Peas      .... 

Peanuts 


Grains. 
Wheat  flour  (white) 
Wheat  bread 
Oatmeal     .... 
Maize  (corn)      .     . 
Rice 


VI.   Vegetables. 

Potatoes     . 
Cabbage     . 


Pro 

TEIDS 

4  OZ. 


.103 
.158 

•235 
.050 

•°37 


.007 
.004 
.005 
.005 

•I25 
.040 
.050 


.20 
.098 

•25 

.181 

.210 

•i75 

•035 

•125 

•335 
.003 


•25 

.217 

.2947 


.110 
.080 
.126 
.100 
.050 


.012 
.02 


Fats 


.708 
•574 

•53 

•51 
.02 


.014 


■035 

.489 
.365 

.029 

.038 
.005 

.040 
.120 

•243 

.910 


.020 
.019 

•465 


.015 

.056 
.067 

.008 


.001 

.030 


Carbohy 

DRATES 


14  OZ. 


•143 
.•16 

.12 

.38 

Sugar 
.045 
.072 
.Q40 
.10 

•15 

•5° 
.20 


.009 


.040 


Starch 

•52 

^•577 
.162 


•703 
.490 
.630 
.706 
.832 


.205 
.058 


2  qt. 


■03 
•03 

.078 

•35 
•54 


•85 
.84 
.86 

.84 
.70 

•75 


•75 

•390 

.278 

.7S0 

.740 

.800 

.870 

•735 
.368 
.060 


.125 

.12 

.02 


.150 
.400 
.150 

•135 
.100 


.767 
.910 


Mineral 

MM  S 


.OI7 
.OI4 


.OO9 


.OO7 
.OO5 
.OO4 
.OO7 
.OO5 


.Ol6 

.023 
.IOI 
.OIO 
.OI2 
.OI5 
.OO7 
.OIO 

•054 
.021 


•°35 
.028 
.028 


.017 
.012 
.030 
.014 
.005 


.009 
.007 


Woody 
Fiber 


.04 
.02 


.04 

•°5 
.01 
.02 


.060 
.032 
•043 


.003 
.003 
.016 
.015 
.040 


.006 
.015 


q6  human  biology 

Studies  based  on  Table. — What  nuts  are  rich  in  protcids  ?  What 
fruits?  What  animal  foods?  What  legumes?  What  grains?  What  foods 
are  rich  in  fats?  What  are  rich  in  carbohydrates?  Which  grains  have 
much  starch?  Which  nut?  Which  fruits  have  much  sugar?  A  family 
was  livingschielly  on  corn  bread,  potatoes,  syrup,  cakes,  and  sweetmeats  : 
what  two  of  the  four  food  stuffs  were  deficient  in  their  diet?  Another 
family  lived  chiefly  on  fat  pork,  bread,  rice,  vegetables,  and  fruit:  which 
food  stuff  was  deficient?  A  dozen  eggs  weigh  i .',  ll>.  Which  give 
cheaper  nourishment,  eggs  at  15  cents  a  dozen  or  beef  at  15  cents  a 
pound?  Which  is  cheapest  among  the  foods  abounding  in  proteid? 
Fat?  Carbohydrates?  Which  is  cheaper  food,  a  pound  of  beef  at  20 
cents  or  a  pound  of  pecans  at  the  same  price?  (Fig.  101.)  What  food 
contains  most  water?  Least  water?  Which  of  the  foods  abounding  in 
proteid  is  costliest?  Cheapest?  Notice  that  nearly  all  foods  contain- 
ing much  proteid  are  costly.  Water  and  woody  fiber  are  not  counted 
as  nutriment.  What  weight  of  nutriment  in  1  oz.  of  cow's  milk  ?  If  a 
quart  of  whole  milk  costs  12  cts.,  what  is  a  quart  of  skimmed  milk 
worth  ? 

How  the  Right  Proportions  of  Fuel  Foods  and  Proteid  are  reached  by 
Different  Nations.  —  Milk  has  an  excess  of  nitrogen,  and  oatmeal  an 
excess  of  carbon ;  oatmeal  and  milk  form  a  popular  food  with  the 
Scotch.  Potatoes  are  mostly  starch  and  water,  and  an  Irishman  who 
tried  to  live  on  potatoes  alone  would  have  to  eat  seven  pounds  a  day 
to  get  enough  proteid.  The  Irish  peasant  keeps  a  cow  and  chickens; 
by  eating  milk  and  eggs  he  gets  along  on  half  the  amount  of  potatoes 
named  above.  The  Mexicans  eat  bread  made  of  corn  meal,  and  supply 
the  proteid  by  using  beans  as  a  constant  article  of  diet.  Hundreds  of 
millions  of  people  in  Asia  (the  Hindus,  Chinese,  and  others)  subsist 
mainly  on  rice,  which  contains  only  five  per  cent  of  proteid  and  no  fat ; 
the  chief  addition  they  make  is  butter,  or  other  fat,  and  beans,  which 
contain  vegetable  proteid. 

Outline  of  Digestion.  —  The  food  is  made  soluble  in  the 
alimentary  canal  and  is  absorbed  by  the  blood  vessels  and 
lymphatics  in  its  walls.  This  canal  is  about  thirty  feet 
long  (Figs.  89,  90)  and  consists  of  — 

(1)  The  mouth,  where  the  food  remains  about  a  minute, 
while  it  is  chewed  and  mixed  with  the  saliva;  the  saliva 
changes  a  portion  of  the  starch  to  malt  sugar. 

(2)  The  gullet,  a  tube  nine  inches  long,  running  from 


FOOD  AND  DIGESTION 


97 


mouth    to    stomach    antf    lying    in    front    of    the    spinal 
column. 

Illustrated  Study  of  Food  Tract. 


Fig.  89. —  Organs  of    Trunk 
from  the  side. 

L,  larynx;  th,  thyroid  gland;  T,  trachea; 
St,  breastbone  ;  C,  heart  ;  D,  dia- 
phragm ;  F,  liver  ;  E,  stomach  ;  /. 
intestine  ;  Co,  colon  ;  R,  rectum  ; 
V,  bladder. 

Question :  Parts  of  which  organs  are  far- 
ther back  than  spinal  column?  Com- 
pare this  figure  with  colored  Fig.  6. 


Fig.  90.  —  Digestive  Organs,  from  the 
front  (liver  turned  up). 

1,  gullet  ;  2,  stomach  ;  3,  spleen  ;  4,  pancreas  : 
5,  liver  (turned  upward)  ;  6,  gall  bladder; 
7,  8,  9,  small  intestine:  9',  junction  of  small 
with  large  intestine  :  10,  caecum  (blind  sac)  ; 
11,  vermiform  appendix  ;  12,  12',  12",  ascend- 
ing, transverse,  and  descending  colon  ;  13, 
rectum  (straight)  just  below  S-shaped  flexure 
of  colon. 

Question:  Compare  with  Fig.  89,  and  colored 
Fig.  6. 


(3)  The  stomach,  a  large  pouch  where  the  food  is  stored, 
and  from  which  it  passes  in  the  course  of  several  hours, 

H 


98 


III' MAX  BIOLOGY 


having  become  semi-liquid,  and  tt*e  proteids  having  been 
partly  digested  by  the  gastric  juice,  an  acid  secretion  from 
the  small  glands  in  the  stomach  walls. 

(4)  The  small  intestine,  a  narrow  tube  more  than  twenty 
feet  long,  where  the  fats  are  acted  upon  for  the  first  time, 
and  where  the  starches  and  proteids  are  also  acted  upon, 
and  where,  after  about  ten  hours,  the  digestion  of  the 
three  classes  of  foods  is  completed  by  pancreatic  juice 
from  the  pancreas,  and  bile  from  the  liver. 

(5)  The  large  intestine,  about  five  feet  long,  where  the 
last  remnant  of  nutriment  is  absorbed,  and  the  indigestible 
materials  in  the  food  are  gathered  together  (Exp.  9). 

The  Teeth.  —  The  main  body 
of  the  tooth  consists  of  bone- 
like dentine,  or  ivory.  Hard, 
shining  enamel  protects  the 
crown,  or  visible  portion.  The 
part  of  the  tooth  beneath  the 
gum  is  called  the  neck,  and  the 
part  in  the  bony  socket  is  called 
the  root.  The  enamel  ends  just 
beneath  the  gum,  where  it  is 
overlapped  by  cement  of  the 
root.  There  is  a  pulp  cavity 
in  every  tooth  (Fig.  91);  it 
contains  pulp  made  up  of  con- 
nective tissue,  with  nerves  and 
blood  vessels  which  enter  at  the 
tip  of  the  root  (Exp.  6). 

The  temporary  set  of  teeth  is 
completed  at  about  two  years  of  age  and  consists  of  twenty 
teeth.  The  teeth  cannot  grow  as  the  jaw  grows,  and  soon 
a  larger  and  permanent  set  starts  to  growing  deeper  in  the 


Cemeot  or  crusta  petrosa 
Alveolar  periosteum  or  root-membrane 

Fig.  91.  — Canine  Tooth  cut 
lengthwise. 


FOOD  AND  DIGESTION 


99 


jaw.  At  the  age  of  twelve  or  thirteen  years  all  the 
permanent  set  have  appeared  except  the  four  wisdom 
teeth,  which  appear  between  the  ages  of  seventeen  and 


3rd  rnolar 


1st  molar 


1st  premolar     Y       Lateral  rncisor 
2nd  molar  2nd  premolar  Ca.ime  Central  incisor 

Fig.  92.  —  The  Permanent  Teeth  in  right  half  of  lower  jaw. 

twenty-five.  The  second  set  not  only  replaces  the  twenty 
of  the  first  set,  but  to  fill  the  larger  jaws  twelve  molars  are 
added,  three  at  the  back  in  each  half  jaw,  making  thirty- 
two  teeth  in  the  second  set  (Exp. 
7).  The  teeth  in  each  quarter  of 
the  mouth,  named  in  order  from 
the  front,  are  :  two  incisors,  one 
canine,  two  premolars,  three  molars. 
Care  of  the  Teeth.  —  The  best 
way  to  care  for  the  teeth  is  to 
keep  the  digestion  perfect.  Perfect 
digestion  tends  to  preserve  the 
teeth,    and    sound    teeth   tend   to 

keep  the  digestion  perfect.  The  teeth  should  be  washed 
regularly.  Prepared  chalk  is  the  best  dentifrice.  Do  not 
rub  across,  but  from  gums  to  teeth,  to  prevent  rubbing  the 
gums  loose  from  the  teeth.  An  unclean  brush  may  har- 
bor germs.  Toothpicks  and  dental  floss  are  useful.  If 
one  eats  only  soft  food,  in  which  the  mill  and  the 
cooking  stove  have  left  no  work  for  the  teeth,  the  teeth 
will  decay ;  for  it  seems  to  be  a  law  of  nature  that 
useless  organs  are  removed.     The  pressure  from  chewing 


Fig.  93. 


Upper  Jaw  with 
Teeth. 


IOO  HUMAN  BIOLOGY 

hard  food  is  an  aid  to  the  teeth  by  helping  the  circulation 
and  nerves  in  the  pulp.  To  take  a  very  hot  or  very  cold 
drink  into  the  mouth  may  cause  the  enamel  to  crack.  If 
a  tooth  aches,  or  a  small  decayed  place  is  found  in  it,  a 
dentist  should  be  consulted  at  once.  A  tooth  is  so  valu- 
able to  the  health  that  no  tooth  should  be  extracted  when 
it  can  be  saved. 

The  process  of  digestion  consists  in  liquefying  the  food 
that  it  may  pass  through  the  walls  of  the  food  tube  into 
the  blood,  and  through  the  walls  of  the  blood  vessels  into 
the  tissues.  It  is  accomplished:  (i)  by  mechanical  means, 
including  the  chewing  muscles,  the  teeth,  and  three  layers 
of  muscles  in  the  walls  of  the  food  tube;  (2)  by  chemical 
means,  or  the  action  of  alkalies  and  acids  upon  the  food ; 
(3)  by  organic  agency,  or  the  action  of  ferments.  A 
ferment  (or  enzyme)  is  a  vegetable  substance  which  has 
the  power  of  producing  a  chemical  change  in  large  quanti- 
ties of  substance  brought  in  contact  with  it,  without  being 
itself  changed.  There  is  one  ferment  secreted  in  the  mouth, 
two  in  the  stomach,  and  three  in  the  small  intestine. 

Digestion  in  the  Mouth.  —  Saliva  is  formed  by  six  glands  : 
one  in  the  cheek  in  front  of  each  ear,  one  at  the  angle  of 
each  lower  jaw,  and  one  pair  is  beneath  the  tongue.  Each 
gland  opens  into  the  mouth  by  a  duct.  Saliva  is  ropy 
because  it  is  mixed  with  mucus  formed  by  the  mucous 
membrane  lining  the  mouth  ;  it  usually  contains  air  bub- 
bles. There  is  a  ferment  in  the  saliva  called  ptyalin,  which 
has  the  power  of  changing  starch  to  malt  sugar.  If  a  bit 
of  bread  is  chewed  for  a  long  time,  it  becomes  sweet, 
because  some  of  the  starch  is  changed  to  sugar.  The  flow 
of  saliva  is  caused  by  chewing,  or  by  the  sight,  or  even  the 
thought,  of  agreeable  food.  Dryness  of  food  is  by  far 
more  powerful  than  anything  else  in  causing  the  saliva  to 


FOOD  AXD  DIGESTION 


IOI 


flow.     Saliva  is  secreted  only  one  fourth  as  fast  when  eat- 
ing oatmeal  and  milk  as  when  eating  dry  toast  (Fig.  94). 


Fig.  94.  —  Cells  of  a  Salivary  Gland 

A,  after  rest,  full  of  granules  ;   B,  after  short  activity  :    C,  after  prolonged  activity,  cells 
shriveled  and  granules  lost. 

Starchy  grains  and  fruits  were  eaten  by  early  man  without  cooking, 
and  required  more  chewing  than  sweet,  ripe  fruits  or  oils  or  proteids. 
Hence  the  saliva  was  given  the  power  of  acting  upon  the  starch,  for 
it  must  remain  in  the  mouth  longer.  The  saliva  is  alkaline ;  and  if 
the  food  is  not  thoroughly  mixed  with  it,  the  stomach  digestion  will 
also  be  imperfect,  for  the  alkaline  saliva  is  necessary  to  excite  an 
abundant  flow  of  gastric  juice  in  the  stomach  (Exp.  1). 

Eating  slowly  is  difficult  because  of  the  grinding  and  cooking  of 
food  ;  hence  the  common  practice  of  overeating.  To  eat  slowly  (1)  do 
not  take  large  mouthfuls ;  (2)  do  not  take  a  second  morsel  until  the 
first  has  been  swallowed  ;  (3)  sit  erect  or  lean  back  after  putting  food 
into  the  mouth  ;  (4)  the  hands  should  lie  idle  most  of  the  time.  To 
lean  fonvard  and  keep  food  traveling  to  the  mouth  like  coal  into  a 
chute  means  overeating  with  all  its  bad  effects. 

Chewing  gum  is  a  coarse  and  impolite  habit,  and  wastes  the  saliva, 
besides  weakening  the  glands  and  irritating  the  stomach  by  the  saliva 
that  is  continually  swallowed.  Chewing  tobacco  has  several  of  these 
disadvantages,  besides  allowing  the  poison  in  the  tobacco  to  be  absorbed 
by  the  mucous  lining  of  the  mouth. 

The  pharynx  (far'inks),  or  throat,  is  a  muscular  bag  sus- 
pended behind  the  nose  and  mouth.  (See  Fig.  89,  also 
Fig.  83.)  There  are  seven  openings  into  the  pharynx:  two 
from  the  nostrils,  two  from  the  ears,  one  each  from  the 
mouth,  larynx,  and  gullet.  Which  of  these  openings  are 
downward  ?     Forward  ?     Lateral  ? 

The  gullet  (or  esophagus)  is  a  muscular  tube  about  nine 


102 


IWMAX  BIOLOGY 


inches  long.  (See  Fig.  89.)  Like  the  rest  of  the  food  tube, 
it  is  lined  with  mucous  membrane.  It  has  two  layers  of 
muscles  in  its  walls,  the  fibers  of  one  layer  running  length- 
wise, and  the  fibers  of  the  other  layer  being  circular.  In 
swal/owing,  the  food  does  not  fall  down  the  gullet  of  its 
own  weight,  but  the  circular  bauds  of  muscle  in  front  of  the 
food  relax,  and  those  behind  it  contract  and  push  it  on  into 
the  stomach.     This  wavelike  motion  is  called  peristalsis. 

The  stomach,  the  greatest  enlargement  of  the  food  tube, 
is  like  a  large  bag  lying  sideways.      It   lies    to    the   left 

side  of  the  abdomen.  The 
walls  of  the  stomach  con- 
sist chiefly  of  muscular 
fibers  which  run  lengthwise, 
crosswise,  and  slantwise, 
making  three  coats  (Exp. 
7,  also  Fig.  95).  As  soon 
as  the  food  reaches  the 
stomach,  the  layers  of 
muscles  begin  to  contract, 
changing  the  size  of  the 
stomach,  first  in  length, 
then  in  breadth,  thus 
churning  the  food  to  and 
fro,  and  mixing  it  with  the 
gastric  juice,  a  fluid  more 
active  than  the  saliva.  For 
as  the  food  enters  the  stom- 
ach, the  mucous  membrane  lining  it  turns  a  bright  red, 
and  many  little  gastric  glands  in  the  lining  begin  to 
secrete  gastric  juice. 

Digestion  in  the   Stomach. — The    stomach    churns    the 
food  from  two  to  four  hours  after  the  meal,  according  to 


Fig.  95.  —  Muscular  and  Other 
Layers  in  Wall  of  Stomach. 

1,  mucous  lining  ;  2,  layer  of  blood  vessels 
and  connective  tissue  ;  3,  muscular 
layers  (involuntary  muscles)  ;  4,  con- 
nective-tissue fibers.     (Peabody.) 


FOOD  AND  DIGESTION 


103 


the  kind  of  food  eaten,  the  way  it  has  been  cooked,  and 
the  thoroughness  with  which  it  has  been  chewed.  The 
gastric  juice  is  chiefly  water,  and  contains  two  ferments 
called  pepsin  and  rennin,  and  a  small  quantity  of  hydro- 
chloric acid.  Rennin  acts  upon  the  curd  of  milk,  and  is 
abundant  only  during  infancy.  Hydrochloric  acid  kills 
germs  that  may  enter  the  stomach,  and  changes  the  food 
which  has  been  made  alkaline  by  the  saliva  into  an  acid 
condition  (Exp.  1).  This  enables  the  pepsin  to  act  upon  the 
protcid  part  of  the  food,  for  pepsin  will  not  act  while  the 
food  is  alkaline.  Gastric  juice  digests  lean  meat,  which  is 
a  proteid  food,  by  first  dissolving  the  connective  tissue  that 
holds  the  fibers  in  place,  and  they  fall  apart ;  it  then  acts 
upon  the  fibers  separately  and  makes  them  soluble.  Like 
human  fatty  tissue  (Fig.  14),  fat  meat  consists  of  cells 
filled  with  fat  and  held  together  by  threads  of  connective 
tissue.  The  cell  walls  and  the  threads,  both  being  proteid, 
are  soon  dissolved  by  the  gastric  juice,  and  the  free  fat  is 
melted  into  oil,  but  still  undigested. 
The  food  is  reduced  in  the  stomach  to 
a  creamy,  half-fluid  mass  called  chyme. 
Where  the  stomach  opens  into  the 
small  intestine,  there  is  a  folding  in  or 
narrowing  of  the  tube  so  as  to  form  a 
kind  of  valve  called  the  pylorus.  After 
the  food  has  been  changed  to  chyme, 
this  fold  relaxes  every  minute  or  two, 
and  allows  some  of  the  chyme  to 
escape  into  the  intestine. 

The  small  intestine  is  about  one  inch 
in  diameter  and  twenty  feet  long,  with      fig.  96.  — a  portion 
many  coils  and  turns  in  its  course  (Fig.         OF    Small    'ntes- 

■'  \       o  tine  cut  open  to  show 

90).     Its  mucous  lining  is  wrinkled  into         the  folds  m  its  lining. 


104  HUMAN  BIOLOGY 

numerous  folds  in  order  to  increase  the  secreting  and 
absorbing  surface  (Fig.  96).  On  and  between  the  folds 
are  thousands  of  little  threadlike 
projections  called  villi  (Fig.  97). 
In  each  villus  are  found  fine  capil- 
laries and  a  small  lymphatic  called 
a  lacteal  (colored  Fig.  2).  The  villi 
are   so   thick    that   they    make   the 

lining  of  the  intestine  like  velvet, 
Fig.     97.  —  Lining     of  .  ,     .  ,         .         . 

Small  Intestine      anc*  enormously  increase  the  absorb- 

magnified,  showing  villi       [ng  surface. 

and  mouths  of  intestinal  .  .        .        . 

glands  Digestion  in  the  Small  Intestine.  — 

This  is  by  far  the  most  active  and 
important  of  the  digestive  organs.  The  mouth  digests 
a  small  part  of  the  starch,  and  the  stomach  digests  a 
small  part  of  the  proteid ;  the  small  intestine  digests 
most  of  the  starch,  most  of  the  proteid,  and  all  of  the 
fats.  The  food  is  in  the  mouth  a  few  minutes,  and  in  the 
stomach  two  or  three  hours  ;  it  is  in  the  small  intestine  ten 
or  twelve  hours.  There  are  thousands  of  small  glands 
called  intestinal  glands  that  open  between  the  villi  (Fig. 
97)  and  secrete  the  intestinal  juice,  which  digests  cane 
sugar.  Besides  these,  there  are  two  very  large  and  active 
glands,  the  pancreas  and  liver,  which  empty  into  the 
intestine  by  ducts. 

The  Pancreas.  —  The  small  intestine  is  the  most  impor- 
tant of  the  digestive  organs,  chiefly  because  it  receives  the 
secretion  from  the  pancreas,  the  most  important  of  diges- 
tive glands.  The  pancreas  is  a  long,  flat,  pinkish  gland 
situated  behind  the  stomach  (see  Fig.  90).  The  pancreatic 
juice  contains  three  powerful  ferments,  one  of  which  (amy- 
lopsin)  digests  the  starches,  another  (trypsin)  digests  pro- 
teids,  and  the  third  (steapsin),  with   the  aid  of  the  bile, 


FOOD   AND   DIG  EST /ON 


105 


breaks  up  the  fats  into  tiny  globules.  Fat  in  small  glob- 
ules floating  in  a  liquid  is  called  an  emulsion;  fresh  milk 
is  an  emulsion  of  cream  (Fig.  98).  Fat  is  not  changed 
to  another  substance 
by  digestion,  but  it  is 
emulsified,  and  in  this 
condition  it  readily 
passes  through  the 
walls  of  the  intestines 
and  is  absorbed  by 
the  lymphatics  called 
lacteals  (colored  Fig. 
5)  found  in  the  villi. 
1 1  then  ascends 
through  the  thoracic 
duct  to  a  large  vein 
at  the  left  side  of  the 
neck  (Fig.  100).  The 
digested  proteid,  starch,  and  sugar  pass  into  the  capillaries 
of  the  portal  vein,  and  go  to  the  liver  on  their  way  to  the 
general  circulation  (Fig.  100).  The  portal  circulation 
empties  into  the  large  ascending  vein  leading  to  the 
right  auricle  (Fig.   100). 

The  Liver.  —  This  large,  chocolate-colored  gland  is  located  just 
beneath  the  diaphragm  on  the  right  side  (Fig.  90,  colored  Fig.  6).  It 
is  on  a  level  with  the  stomach,  which  it  partly  overlaps  in  front.  The 
liver  has  three  important  functions:  (1)  //  is  a  storeroom;  digested 
sugar  and  starch  are  stored  in  it  as  a  substance  called  liver  starch  (or 
gly'cogen).  (2)  //  is  a  guardian,  and  destroys  poisonous  substances 
which  may  be  swallowed,  and  which  would  otherwise  enter  the  blood. 
Twice  as  much  morphine  or  other  poison  is  necessary  to  kill  a  man 
when  it  is  taken  by  the  mouth  and  passes  through  the  liver  as  when  it 
is  injected  through  the  skin.  Alcohol,  morphine,  coffee,  and  drugs  are 
partly  burned  up  in  the  liver.  (3)  //  is  a  gland,  and  secretes  bile. 
The  bile  is  made  chiefly  from  waste  products  and  impurities  in  the 


Fig. 


—Junction  of  Large  and 
Small  Intestine. 


io6 


HUMAN  BIOLOGY 


blood;  it  is  an  excretion.  Although  an  excretion,  it  is  of  use  on  its 
way  oul  of  the  body.  It  is  alkaline  and  helps  to  neutralize  the  acid  in 
the  chyme;  it  excites  the  peristalsis,  or  wavelike  motion,  of  the  intes- 
tines, and  it  aids  the  pancreatic  juice  to  emulsify  the  fats. 

The  large  intestine,  or  colon,  is  about  two  and  one  half 
inches  in  diameter  and  five  feet  long.  The  small  intestine 
joins  it  in  the  lower  right  side  of  the 
abdomen  (Fig.  90).  There  is  a  fold, 
or  valve,  at  the  juncture,  and  just 
below  the  juncture  there  is  a  tube 
attached  to  the  large  intestine,  called 
the  appendix,  which  sometimes  be- 
comes inflamed,  causing  a  disease 
called  appendicitis  (Figs.  90,  98). 
The  appendix  is  a  vestigial  (vesti- 
gium, trace)  or  rudimentary  organ, 
long  since  useless.  Absorption  of 
the  watery  part  of  the  food  continues 
in  the  colon,  but  the  colon  secretes  no 
digestive  fluid.  The  undigested  and 
innutritious  parts  of  the  food  are  regu- 
larly cast  out  of  the  colon.1  The  peri- 
tone'  nm  is  a  membrane  with  many  folds 
that  supports  the  food  tube  (Fig.  99). 
Absorption.  —  The  way  in  which  the  various  digested 
foods  are  absorbed  has  been  stated  in  several  preceding 
topics.  What  is  the  name  of  the  organs  of  absorption  in 
the  small  intestine  ?  Which  of  the  following  pass  into  the 
lacteals,  and  which  into  the  capillaries  of  the  portal  vein  : 
sugar,  digested  proteid,  emulsified  fats  ?  Water  and  salt 
need   no  digestion,    and  are   absorbed  all  along  the  food 

1  No  truly  refined  person  will  allow  business,  pleasure,  haste,  or  neglect  to 
interfere  with  regular  attention  to  emptying  the  colon.  This  is  more  neces- 
sary for  real  cleanliness  than  regular  baths. 


Fig.  99. —  Diagram  of 
Trunk  to  show  the 
many  folds  of  the  peri- 
toneum supporting  the 
liver,  stomach,  and  in- 
testines. 


FOOD  AND  DIGESTION 


107 


tube,  the  absorption  beginning  even  in  the  mouth.  What 
reasons  can  you  give  for  the  absorption  of  food  being 
many  times  greater  in  the  small  intestine  than  in  the 
stomach  ?  Through  what  large  tube  is  the  fat  carried  in 
passing  from  the  lacteals  to  the 
veins  ?  Into  what  large  vein  do  all 
the  capillaries  that  take  part  in  ab- 
sorption empty  ?  (Colored  Fig.  5.) 
What  is  the  provision  for  storing 
the  sugar  so  that  it  will  not  pass 
suddenly  into  the  blood  after  a 
meal,  but  may  be  given  to  the  blood 
gradually  ?  Food  is  assimilated,  or 
changed  into  living  matter  (proto- 
plasm), in  the  cells.  Blood  and 
lymph  (except  the  white  corpuscles) 
are  not  living  matter.     (Fig.  100.) 


Fig.  100.  —  The  Two 
Paths  of  Food  Absorp- 
tion. Thoracic  duct  (for 
fats)  ;  through  the  portal 
vein  and  liver  (for  all 
other  foods). 


Thought  Questions.  The  Digestive 
Organs.  —  1.  In  which  of  the  digestive 
organs  is  only  one  kind  of  secretion  fur- 
nished by  glands?  2.  In  which  organ 
are  three  kinds  of  secretions  furnished  by 
glands?  3.  Which  class  of  food  goes 
through  the  lymphatics  ?  4.  Which  classes  of  foods  go  through  the 
liver  ?  5.  Which  classes  of  foods  are  digested  in  only  one  organ  ? 
6.  Which  classes  of  foods  are  digested  in  two  organs  ?  7.  Which 
division  of  the  food  tube  is  longest  ?  Broadest  ?  Least  active  ? 
Most  active  ?  8.  Soup  is  absorbed  quickly ;  why  does  eating  it  at 
the  beginning  of  a  meal  tend  to  prevent  overeating? 

Hygienic  Habits  of  Eating.  —  In  hot  weather  much 
blood  goes  to  the  skin  and  little  to  the  food  tube,  and  di- 
gestion is  less  vigorous.  Hearty  eaters  suffer  from  heat 
in  summer  because  of  much  fuel,  and  because  the  blood  is 
kept  away  from  the  skin  where  it  would  become  cool  and 
then  cool  the  whole  body.     Some  persons  believe  that  the 


IOS  HUMAN  BIOLOGY 

stomach  should  be  humored  and  given  nothing  that  it  di- 
gests with  difficulty  ;  others  believe  that  it  should  be  gradu- 
ally trained  to  digest  any  nutritious  food.  Some  believe  that 
no  animal  food  should  be  eaten  ;  others  believe  that  animal 
food  is  as  valuable  as  any.  Some  believe  that  all  food 
should  be  eaten  raw,  but  this  would  irritate  a  delicate 
stomach.  It  is  doubtless  best  to  use  no  stimulant,  either 
tea  or  coffee,  pepper  or  alcohol.  Some  eat  fast  and  drink 
freely  at  meals  ;  it  is  better  to  eat  slowly  and  drink  very 
little  or  none  at  all  while  eating,  nor  soon  afterwards. 
Some  eat  five  meals  a  day,  and  between  meals  if  anything 
that  tastes  good  is  offered  them  ;  others  eat  only  two  or 
three  meals  a  day,  and  never  between  meals,  thus  allow- 
ing the  digestive  organs  time  to  rest.  Some  omit  break- 
fast and  some  omit  supper.  Some  prepare  most  of  the 
food  with  grease  ;  this  is  a  tax  upon  digestion.  Physical 
workers  often  believe  in  eating  the  peelings  and  seeds  of 
fruits,  and  partaking  freely  of  weedy  vegetables,  such  as 
cabbage,  turnip  tops,  string  beans.  Mental  workers  usually 
try  to  reject  all  woody  fiber  and  indigestible  pulp  from  the 
food  before  swallowing  it.  Some  eat  large  quantities  of 
food  and  digest  a  small  portion  ;  others  eat  little  but  digest 
nearly  all. 

The  Power  of  Adaptation  of  the  Digestive  Organs.  —  Of  course 
some  habits  of  eating  are  better  for  the  health  than  others,  yet  the  un- 
desirable ways  often  bring  so  little  injury  that  they  are  not  discontinued. 
This  shows  that  the  food  tube  has  great  powers  of  adaptation  to  dif- 
ferent conditions.  But  there  are  limits  to  this  adaptation  ;  there  is  an 
old  saying  that  what  is  one  man's  meat  is  another  man's  poison.  A 
brain  worker  cannot  follow  the  same  diet  as  a  field  hand  without  work- 
ing at  a  disadvantage.  An  irritable  stomach  may  be  injured  by  coarse 
food  that  would  furnish  only  a  healthful  stimulus  to  a  less  sensitive  one. 
A  business  man  who  has  little  leisure  at  noon  should  take  the  heaviest 
meal  after  business  hours.  In  general,  it  may  be  said  that  it  does  not 
make  so  much  difference  what  is  eaten  as  how  it  is  eaten,  and  how 


FOOD  AND  DIGESTION  109 

much  is  eaten.     There  is  a  common  tendency  to  exaggerate  the  im- 
portance of  dietetics. 

Thought  Questions.  Indigestion. —  I.  A  Fetid  Breath.  1.  Name 
three  causes  of  bad  breath.  2.  Let  us  investigate  whether  indigestion 
could  cause  a  bad  breath.  In  what  kind  (two  qualities)  of  weather 
does  meat  spoil  the  quickest?  3.  Suppose  that  meat  or  other  food  is 
put  into  a  stomach  with  its  gastric  glands  exhausted  and  its  muscular 
walls  tired  out,  what  will  be  the  rate  of  digestion,  and  what  might  hap- 
pen to  the  food  ?  4.  Odorous  contents  of  the  stomach  {e.g.  onion) 
can  be  taken  by  the  blood  to  the  lungs  where  it  will  taint  the  breath. 

After  answering  the  above  questions,  write  in  a  few  words  how  indi- 
gestion may  cause  a  bad. breath. 

II.  A  Coated  or  Foul  Tongue.  1.  When  the  doctor  visits  you,  at 
what  does  he  first  look  ?  2.  What  sometimes  forms  on  old  bread  ? 
(p.  158.)  3.  Do  you  think  such  a  growth  possible  on  undigested 
bread  in  the  stomach  ?  4.  The  microscope  shows  the  coating  on  the 
bread  to  be  a  growth  of  mold.  If  it  forms  on  the  walls  of  the  stomach, 
it  may  extend  to  what  ? 

III.  Stomach  Ache.  1.  How  can  you  tell  whether  fruit  preserved 
in  a  sealed  glass  jar  is  fermenting  ?  2.  What  connection  is  there  be- 
tween belching  after  eating  too  freely  of  sweet  or  starchy  food,  and  the 
observation  above  ?  3.  A  muscle  gives  pain  when  it  is  stretched. 
Why  does  belching  sometimes  give  relief  to  an  uneasy  stomach  ? 
4.    Can  you,  by  using  these  facts,  explain  a  cause  of  stomach  ache  ? 

For  what  Kind  of  Man  were  the  Human  Digestive  Organs  created  ?  — 
That  food  is  best  to  which  the  food  tube  has  been  longest  accustomed. 
It  would  be  of  the  greatest  value  as  a  guide  to  diet  if  we  knew  the  food 
eaten  by  early  man  during  the  many  ages  when  he  led  a  wild  life  in  the 
open  air.  The  organs  of  early  man  were  doubtless  perfectly  adapted  to 
the  life  he  led.  The  food  tube  is  adapted  to  the  needs  of  those  long 
ages,  for  a  few  centuries  of  civilization  cannot  change  the  nature  of  the 
digestive  organs  ;  yet  some  people  disregard  natural  appetites  and  try 
to  force  the  digestive  organs  to  undergo  greater  changes  in  a  few 
months  than  centuries  could  bring  about. 

To  test  whether  an  Article  of  Food  belonged  to  Man's  Original  Diet. 
—  Scientists  agree  that  the  human  race  began  in  a  warm  countrv : 
that  early  man  was  without  gristmills,  stoves,  orjire,  and  ate  his  food 
raw.  If  an  article  of  food  is  pleasant  to  the  taste  in  its  raw,  pure  state. 
there  is  little  doubt  that  it,  or  a  similar  food,  was  eaten  by  primitive 
man  before  he  knew  the  use  of  fire  in  preparing  his  food.  Applv  this 
test  to  the  following  foods,  underlining  those  foods  that  pass  the  test  : 
apples,  bananas,  lettuce,  turnip  greens,  turnips,  fruits,  nuts,  beef,  fowls, 


I  IO 


HUMAN  BIOLOGY 


Beef 


Bread 


Bananas 


Nuts 


Potatoes 


Lettuce 


eggs,  oysters,  green  corn,  cabbage,  pork, 
watermelons,  grains,  crabs,  fish,  white  or 
Irish  potatoes,  yams,  tomatoes. 

The  Order  in  which  Man  increased  his  Bill 
of  Fare.  —  Flesh-eating  animals  have  a  short 
food  tube,  as  their  food  is  digested  quickly; 
they  have  long,  pointed  teeth  for  tearing,  sharp 
claws  for  holding,  and  a  rough  tongue  for  rasp- 
ing meat  from  the  bones.  Man's  even  teeth, 
long  food  tube,  soft  and  smooth  tongue,  and 
flattened  nails,  indicate  that  he  is  suited  for  a 
diet  largely  vegetable  (see  Table,  p.  iii).  The 
race  at  first  probably  ate  tree  fruits}  both  nuts 
and  fleshy  fruits  (Fig.  101).  Because  of 
famine,  or  after  migration  to  colder  climates, 
and  after  learning  the  use  of  fire,  the  race  prob- 
ably began  to  use  flesh  for  food.  Afterward 
the  hunters  became  farmers  and  learned  to 
cultivate  grain,  which  formed  a  most  important 
addition  to  the  food  supply,  and  made  possible 
a  dense  population.  Coarse,  woody  foods,  like 
the  leaves  and  stems  of  herbs,  were  probably 
added  last  of  all.  Woody  fiber  (cellulose)  can 
be  digested  by  cattle,  but  it  cannot  be  digested 
by  man. 

The  Natural  Guide  in  Eating  is  Taste. 
Man  should  preserve  his  taste  uncorrupted  as, 
next  to  his  conscience,  his  wisest  counselor 
and  friend.  It  has  been  developed  and  trans- 
mitted through  countless  ages  as  a  precious 
heritage.  Simple  food  is  more  delicious  to 
people  with  natural  tastes  than  the  most  arti- 
ficial concoctions  are  to  those  with  perverted 
taste. 

Animal  Food.  — Th&Jlcsh  of  animals 

furnishes   proteid   and  fat  (Fig.    102). 

As    cooking   coagulates    and    hardens 

1  See  Genesis  i.  29.  Some  raw  food  should  be 
eaten  daily.  Pecans  are  the  most  digestible  of  all 
nuts.  A  half  dozen  or  more  eaten  regularly  for 
breakfast  will  prevent  constipation  or  cure  it  in  ten 
days  or  less. 


FOOD  AND  DIGESTION 


III 


albumin,  raw  or  half-cooked  meat  is  said  to  be  more  diges- 
tible than  cooked  meat ;  but  meat  that  is  not  thoroughly 


Fig.  102.  —  Diagram  showing  Cuts  of  Beef. 

cooked  is  dangerous  because  it  may  contain  trichinae 
("Animal  Biology,"  p.  50)  and  other  parasites.  Lean  meats 
contain  much  proteid.  Some  persons  who  cannot  easily 
digest  starch  and  sugar  because  of  fermentation  eat  fat 
for  a  fuel  food.  Beef  tea  and  beef  extracts  contain  but  a 
small  part  of  the  proteid  in  meat  and  all  of  the  waste 
matter,  including  urea. 


Mammals 
compared 

Carnivora,  or 
flesh-eaters 

Herbivora,  OR 

HERB-EATERS 

Omnivora,  or 
all-eaters 

Frugivora,  or 
fruit-eaters 

Examples. 

Cat,  dog,  lion. 

Cow,  horse. 

Hog,  peccary. 

Man,  monkey. 

Length  of 
food  tube. 

3  times  length 
of  body. 

30  times  length 
of  body. 

10  times  length 
of  body. 

12  times  length 
of  head-trunk. 

Teeth. 

Pointed       for 
tearing  flesh. 
Canine  teeth 
long. 

Layers          of 
enamel      and 
dentine  form- 
ing ridges. 

Cutting    teeth 
project.       Ca- 
nines        form 
tusks. 

Teeth  even, 
close  together. 
Canines  not 
projecting. 

Digits. 

Sharp  claws. 

Hoofs. 

Hoofs. 

Flattened  nails. 

Colon. 

Smooth. 

Sacculated. 

Smooth. 

Sacculated. 

I  12  HUMAN  BIOLOGY 

Milk  of  cows  is  improperly  called  a  perfect  food  by  some  writers. 
Although  it  contains  the  four  classes  of  food  stuffs,  the  proteid  is  in  ex- 
cess, the  fuel  food  being  deficient.  Buttermilk  is  more  digestible  than 
sweet  milk.  Buttermilk  and  sugar  form  a  valuable  food  for  infants. 
Skimmed  milk  still  contains  the  proteid,  the  most  nutritious  part  of 
the  milk.  Sour  milk,  or  "clabber,"  and  curds  pressed  into  "cottage 
cheese  "are  more  digestible  than  sweet  milk.  Cream  is  more  easily 
digested  than  butter,  which  is  a  solid  fat.  Cheese  is  a  very  concentrated 
proteid  food,  and  should  be  eaten  sparingly.  Eggs  are  a  valuable  food. 
Is  there  more  proteid  or  fat  in  eggs?  (See  Table.)  Pork  and  veal 
are  the  most  indigestible  of  meats.  FisJi  is  nearly  as  nutritious  as  meat. 
There  used  to  be  a  supposition  that  fish  nourished  the  brain  because 
it  contains  phosphates  ;  but  there  are  more  phosphates  in  meat  than 
in  fish,  and  more  in  grains  than  in  meat. 

Grains  contain  considerable  proteid  (gluten),  but  they  especially 
abound  in  starch.  Wheat  flour  contains  more  gluten  than  corn  meal, 
hence  it  is  more  sticky,  and  retains  the  bubbles  of  gas  so  that  the 
dough  rises  well  in  bread  making.  Eggs  are  sometimes  added  to 
corn  meal  to  make  it  sticky  and  cause  it  to  rise  well.  Which  grain  has 
the  largest  percentage  of  oil?  (See  Table.)  Of  starch  ?  Of  gluten? 
Which  is  poorest  in  gluten?  Grains  may  be  made  to  resemble  fruit 
by  long  cooking  at  a  high  temperature  (3000  Fahr.),  for  their  starch  is 
thus  changed  to  dextrin,  a  substance  resembling  sugar.  You  learned 
that  the  starch  of  fruit  is  turned  into  sugar  as  the  sun  ripens  it.  Dex- 
trin is  yellow  and  gives  the  dark  color  to  toasted  bread.  It  is  changed 
to  sugar  almost  instantly  when  brought  in  contact  with  saliva.  It  is 
used  as  a  paste  on  postage  stamps. 

Vegetables  contain  much  water  and  woody  fiber.  White  potatoes  we 
underground  stems  and  are  one  fifth  starch.  Yams,  or  sweet  potatoes, 
resemble  roots,  and  contain  both  starch  and  sugar.  Beans  and  peas 
are  very  nutritious.  They  have  been  called  "  the  lean  meat  of  the 
vegetable  kingdom.1'  They  require  boiling  for  several  hours.  If  the 
skins  are  removed  by  pressing  them  through  a  colander,  they  are  very 
easy  of  digestion.  This  puree  of  beans  makes  delicious  soup.  "Hull- 
less  beans"  and  "  split  peas"  are  also  sold  by  grocers. 

Practical  Questions.  —  1.  Clothing  and  shelter  for  man  or 
beast  economize  what  kind  of  food?  2.  Why  should  bread  remain 
longer  in  the  mouth  than  meat?  3.  In  snowballing,  what  is  the  ap- 
pearance of  the  hands  when  they  itch  from  cold?  Extreme  cold  irri- 
tates and  congests  the  stomach  more  quickly  than  it  does  the  hands. 
Why  is  it  that  ice  water  does  not  satisfy  the  thirst,  but  often  produces 
a  craving  to  drink  more  water?     4.    Should  biscuits  having  a  yellow 


FOOD  AND  DIGESTION 


113 


tint  or  dark  spots  due  to  soda  be  eaten  or  thrown  away?  5.  Why, 
during  an  epidemic,  are  those  who  have  used  alcohol  as  a  beverage 
usually  the  first  to  be  attacked?  6.  Do  you  buy  more  wood  (cellulose) 
when  you  buy  beans  or  when  you  buy  nuts?  (p-95-)  7.  Do  you  buy 
more  water  when  you  buy  bread  or  when  you  buy  meat?  8.  Why  do 
people  who  live  in  overheated  rooms  often  have  poor  appetites?  (p.  90.) 
9.  Explain  how  the  stomach  may  be  weakened  by  the  eating  of  predi- 
gested  foods.  10.  Whyare  deep  breathing  and  exercises  that  strengthen 
weak  abdominal  walls  better  for  the  liver  than  are  drugs?  (See  p.  58.) 
11.  Sixty  students  at  the  University  of  Missouri  found  by  doing  with- 
out supper  that  their  power  to  work  was  greater,  their  health  better, 
and  many  of  them  gained  in  weight.  So  they  ate  only  two  meals 
thereafter.  If  sixty  plowboys  tried  the  experiment,  would  the  result 
probably  have  been  the  same?  12.  If  a  person  began  to  eat  less  at 
each  meal,  or  only  ate  one  meal  a  day,  yet  gained  in  weight,  should  he 
agree  with  a  friend  who  told  him  he  was  starving  himself  ?  Should  he 
agree  if,  instead  of  gaining,  he  lost  weight?  13.  Why  is  half-raw  or 
soggy  bread  harder  to  digest  than  the  raw  grain  itself  ?  Which  would  be 
thoroughly  chewed  and  cause  a  great  flow  of  saliva  ?  14.  Ask  a  fat  person 
whether  he  drinks  much  water.  A  lean  person.  15.  Why  is  one  whose 
waist  measures  more  than  his  chest  a  bad  life  insurance  risk  ?  16.  What 
changes  in  habits  tend  to  make  a  rheumatic  middle-aged  person  more 
youthful?     17.    How  is  the  ingenious  "  tireless  cooker "  constructed? 

Atwater's  Experiments  with  Alcohol.  —  A  few  years  ago 

Professor  Atwater  proved  that  if  alcohol  is  taken  in  small 

quantities,  it  is  so  completely  burned  in  the  body  that  not 

over  two  per  cent  is  excreted.     He  inferred  that  it  is  a 

food,  since  it  gives  heat  to  the  body  and  possibly  gives 

energy  also.     His  experiments  did  not  show  whether  any 

organ  was  weakened  or  injured  by  its  use.     As  alcohol  is 

chiefly   burned    in    the  liver,    it    probably   cannot  supply 

energy  as  is  the  case  with  food  burned  in  nerve  cell  and 

muscle  cell.     The  heat  supplied  by  its  burning  is  largely 

lost  by  the  rush  of  blood  to  the  skin  usually  caused  by 

drinking  the  alcohol.     Dr.  Beebe,  unlike  Professor  Atwater, 

experimented  upon  persons  who  had  never  taken  alcohol, 

and  whose  bodies  had  not  had  time  to  become  trained  to 

resist  its  evil  effects.     He  found  that  it  caused  an  increased 


I  1 4  HUMAN  BIOL OGY 

excretion  of  nitrogen.  When  the  body  became  used  to  it, 
this  decreased,  but  the  proteid  excreted  by  the  kidneys 
contained  an  abnormal  amount  of  a  harmful  material  called 
uric  acid.  Uric  acid,  a  substance  which  is  present  in 
rheumatism  and  other  diseases,  is  usually  destroyed  by 
the  liver.  As  the  burden  of  destroying  the  alcohol  falls 
chiefly  upon  the  liver,  it  is  not  surprising  to  find  that  it  is 
so  weakened  and  injured  by  alcoholic  drink  that  it  cannot 
fully  perform  its  important  functions.  Bright's  disease 
and  other  diseases  accompanied  by  uric  acid  are  more 
frequent  among  persons  who  use  alcoholic  drinks. 

Definition  of  Food.  — A  food  is  anything  which*  after  being  absorbed 
by  the  body,  nourishes  the  body  without  injuring  it.  Does  alcohol  or 
tobacco  come  within  this  definition? 

Advantages  of  Good  Cooking.  —  Taste  and  flavor  may  be  developed : 
parasites  are  killed  ;  taste  may  be  improved  by  combining  foods  ;  starch 
grains  are  burst  and  the  food  softened.     Thus  digestion  is  aided. 

Disadvantages  of  Bad  Cooking.  —  Proteid  foods  are  hardened  ;  flavors 
may  be  driven  off;  too  many  kinds  of  food  may  be  mixed;  cooked 
vegetables  are  more  likely  to  ferment  than  raw  vegetables ;  palatable 
food  may  be  made  tasteless  or  soggy  or  greasy  ;  soda  and  other  indiges- 
tible ingredients  may  be  added ;  food  may  be  so  highly  seasoned  as  to 
cause  catarrh  of  the  stomach ;  it  may  so  stimulate  the  appetite  that  so 
much  is  eaten  as  to  overload  the  stomach.  Food  may  be  made  so  soft 
that  it  cannot  be  chewed  and  is  eaten  too  rapidly:  for  instance,  bread 
shortened  with  much  grease. 

The  Five  Modes  of  Cooking.  —  Food  may  be  cooked  (i)  by  heat 
radiating  from  glowing  coals  or  a  flame,  as  in  broiling:  (2)  by  hot 
air,  as  baking  in  a  hot  oven :  (3)  by  boiling  in  hot  water  or  grease,  as 
frying:   (4)   by  hot  water,  not  boiling,  as  in  stewing;    (5)  by  steaming. 

Radiant  Heat.  —  Toasting  bread  and  broiling  meat  are  examples. 
The  meat  should  be  turned  over  every  ten  seconds  to  send  its  juices 
back  and  forth,  thus  preventing  their  escape,  and  broiling  the  meat 
in  the  heat  of  its  own  juices.  Roasting  is  an  example  of  this 
method  combined  with  the  second  method.  The  fire  should  be  hot  at 
first  in  order  to  sear  the  outside  of  the  meat  and  prevent  the  escape  of 
its  juices.  If  the  piece  roasted  is  small,  the  hot  fire  may  be  kept  up ; 
but  if  it  is  large,  a  longer  time  is  required,  and  the  fire  should  be 
decreased,  otherwise  the  outside  will  be  scorched  before  the  central  part 


FOOD  AND  DIGESTION  115 

becomes  heated.     White,  or  Irish,  potatoes  roasted  with  their  skins  on 
best  retain  their  flavor  as  well  as  valuable  mineral  salts  (potash,  etc.). 

Cooking  by  hot  air  can  only  be  used  with  moist  foods.  Baking  is  an 
example.  Foods  only  slightly  moist  are  made  hard,  dry,  and  unpalatable 
if  cooked  by  this  method. 

Cooking  by  Boiling.  —  To  boil  potatoes  so  as  to  make  them  mealy 
instead  of  soggy,  the  water  should  be  boiling  when  they  are  put  in,  and 
after  they  are  cooked  the  water  should  be  poured  off  and  the  pot  set  on  the 
back  of  the  stove  for  the  potatoes  to  dry.  Boiling  onions  drives  off  the 
acrid,  irritating  oil.  Rapid  boiling  of  vegetables  gives  less  time  for  the 
water  to  dissolve  out  the  nutrients.  (See  Steaming.)  Raw  cabbage  is 
treated  by  the  stomach  as  a  foreign  substance,  and  sent  promptly  to  the 
intestine ;  cabbage  boiled  with  fat  may  remain  in  the  stomach  for  five 
hours.  Instead,  it  should  be  boiled  in  clear  water  for  twenty  minutes. 
Beans  and  peas  require  several  hours'  boiling. 

Cooking  in  hot  liquid  below  the  boiling  point  is  better  than  boiling. 
In  frying  meat,  it  should  be  put  in  hot  grease  that  a  crust  may  be  formed 
to  prevent  the  grease  from  soaking  in.  Grease  much  above  boiling  point 
becomes  decomposed  into  fatty  acids  and  other  indigestible  products. 
Hence  butter  is  more  digestible  than  cooked  fats.  In  whatever  way 
meat  is  cooked,  it  should  never  be  salted  until  the  cooking  is  finished 
or  the  salt  will  draw  out  the  juices  which  flavor  it.  Eggs  may  be 
cooked  by  placing  them  in  boiling  water  and  setting  the  kettle  off  the 
stove  at  once  to  cool.  A  finely  minced  hard-boiled  egg  is  as  digestible 
as  a  soft-boiled  egg.  Since  boiling  for  more  than  a  very  few  minutes 
coagulates  and  hardens  albumin,  there  is  no  such  thing  as  boiling  meat 
without  making  it  tough  and  leathery  throughout.  It  may  be  stewed, 
a  process  which  belongs  to  the  next  method. 

In  stewing  meat,  it  may  be  plunged  into  boiling  water  for  a  few  min- 
utes; this  coagulates  the  albumin  on  the  surface.  The  fire  should  then 
be  reduced,  or  the  vessel  set  on  the  cooler  part  of  the  stove,  or  a  metal 
plate  should  be  placed  beneath  it,  that  the  water  may  barely  simmer. 
The  water  should  show  a  temperature  of  185  or  1903  if  tested  with  a 
thermometer.     A  piece  of  meat  cooked  in  this  way  is  tender  and  juicy. 

Cooking  by  steam  requires  a  double  vessel  or  a  vessel  with  a  per- 
forated second  bottom  above  the  water,  through  which  the  steam  may 
rise  to  the  food  that  is  to  be  steamed.  Steamed  vegetables  have  a  better 
flavor  and  are  more  nutritious  than  those  cooked  in  any  other  way.  A 
steamer  is  different  from  a  double  boiler.  Oatmeal  should  be  cooked 
for  at  least  forty  minutes,  and  it  is  more  digestible  if  steamed  for  several 
hours  until  it  is  a  jelly.  To  do  this,  it  may  be  cooked  during  the  prepa- 
ration of  two  meals.  Cooking  that  leaves  it  lumpy  and  sticky  is  a  dis- 
advantage, and  makes  it  more  likely  to  ferment  than  if  eaten  raw. 


Il6  HUMAN  BIOLOGY 

Thought  Questions.  Cooking.  —  Meat.  1.  In  making  soup,  why 
should  the  meat  be  put  in  while  the  water  is  cold?  2.  In  roasting 
meat,  why  should  the  oven  be  hot  at  first,  and  more  moderate  after- 
ward? How  should  you  regulate  the  temperature  in  boiling  or  stewing 
meat?     3.    What  happens  to  salt  or  anything  salty  on  a  cloudy,  damp 

day?     This  is  because  the  salt  attracts .     This  shows  that  meat 

should  not  be  salted  until  after  it  has  been  cooked,  because  if  salted  be- 
fore   .     4.   Very  tough  meat  should  be  b — ed  or  st — ed.     5.    Meat 

may  be  prevented  from  becoming  grease-soaked  when  frying  by  having 
the  grease  very ,  use  very .  simply  greasing  the . 

6.    Bread.     Bread  crust  causes  the to  be  used  more  and  cleans 

them.     It  will  not together  in  the  stomach  like  the  crumb.     It 

increases  the  quantity  of  the  .  and   is  more  digestible  than  the 

crumb,  since  the  has  been   changed   by   slow   heat   to  (p. 

112).  Therefore  loaves  or  biscuit  should  be  (large  or  small?)  and  they 
should  (touch  or  be  separated?)  in  a  pan.  7.  How  can  you  tell 
whether  the  oven  has  been  too  hot  while  the  bread  was  baking?  8. 
Why  can  you  tell  best  about  the  digestibility  of  bread  when  you  are 
slicing  it?  9.  Regulating  the  heat  is  the  greatest  art  of  the  cook. 
How  may  the  temperature  of  the  oven  be  lowered  by  means  of  the 
damper?     The  draft?     The  fuel? 

Exercises  in  Writing.  —  Story  of  a  Savage  who  went  to  dwell  in 
a  City  (his  trouble  with  artificial  ways).  Is  it  easier  to  learn  Physi- 
ology or  to  practice  it?  How  to  make  Bread.  Describe  People  seen 
in  an  Audience  (tell  what  their  appearance  suggests).  A  Scene  at  a 
Dinner  Table.  Thoughts  of  a  Physician  on  his  Round  of  Visits. 
A  Good  Cook.  A  Bad  Cook.  Is  Cooking  a  Greater  Accomplishment 
than  Piano  Playing?  Common  Causes  of  Illness.  The  Influence  of 
Imperfect  Digestion  upon  the  Other  Organs.  Effect  of  Lack  of 
Muscular  Activity.  The  Way  of  the  Transgressor  is  Hard.  What 
Fools  we  Mortals  be!  Health  Fads.  Temperance  in  all  Things. 
The  Right  Way  the  Easiest.  Looking  Back.  Looking  Forward. 
Hygiene  of  the  Schoolroom.  Patent  Medicines.  Microbes.  Mind 
Cure.  Nervous  Women.  Dissipated  Men.  How  a  Friend  of  mine 
lost  his  Health.  Why  a  Friend  of  mine  is  Sound  and  Strong.  Tobacco. 
It  never  pays  to  neglect  the  Health.  Which  does  more  Harm,  an  Ig- 
norant Cook  or  an  Ignorant  Janitor?  A  Visit  to  a  Sick  Room.  Alco- 
hol and  Crime.  Natural  Instincts  and  Appetites;  how  preserved, 
how  lost.  A  Lesson  about  Alcohol  based  upon  the  Morning  News. 
Effects  of  Alcohol  upon  the  Greatness  of  our  Country  (workmen,  voters, 
soldiers,  children).     Adam's  Apothecary  Shop.     Adam's  Ale  (water). 


CHAPTER   VIII 

THE   NERVOUS    SYSTEM 

Review  Questions  introducing  this  Subject.  —  What  is  a  cell?  What 
are  the  five  supporting  tissues?  What  are  the  two  master  tissues? 
Why  are  they  so  called?  What  kind  of  cells  have  many  branches? 
Does  the  food  ever  come  in  contact  with  the  salivary  glands?  When 
you  look  at  a  basket  of  apples,  the  sight  "  makes  your  mouth  water.7' 
Is  there  a  connection  between  the  eye  and  the  mouth?  What  two  tis- 
sues enable  the  skin  to  blanch  and  to  blush  ?  Do  the  different  organs 
share  the  blood  in  the  same  proportions  at  all  times?  How  can  this 
proportion  be  changed?  How  is  the  brain  protected  from  injury? 
How  is  the  spinal  cord  protected?  Is  the  hole  for  the  spinal  cord 
through  the  main  body  of  the  vertebra,  or  behind  the  main  body? 

Harmonious  Activity.  —  Strike  suddenly  at  the  eye  of 
another,  and  the  lids  fall  to  protect  it,  and  the  hands  rise 
to  ward  off  the  blow.  If  a  grain  of  dust  gets  into  the  eye, 
the  tear  glands  form  tears  to  wash  it  out.  If  you  touch 
the  hand  unexpectedly  to  a  hot  iron,  the  muscles  of  the 
arm  jerk  the  hand  away.  If  the  foot  of  a  sleeping  person 
is  tickled,  the  muscles  of  the  leg  pull  it  away.  Many 
muscles  cooperate  in  the  act  of  running.  If  the  human 
being  were  merely  an  assemblage  of  working  organs,  the 
organs  might  act  independently,  and  there  would  be  such 
confusion  that  the  body  would  be  powerless,  and  life  could 
not  be  maintained.  The  nervous  system  enables  the  or- 
gans to  work  together  for  the  common  good.  Why  does 
an  ameba  not  need  a  nervous  system  ? 

The  Need  of  Nerve  Centers  as  well  as  Nerves.  —  If  there 
were  no  central  office  in  a  telephone  system  of  one  thou- 
sand subscribers,  then  every  subscriber,  in  order  to  com- 

117 


n8 


HUMAN  BIOLOGY 


M/c/et/m 
-Me 


-Wtfe 


^o^ 


Mxfe- 


FlG.  103.  —  Sliowing  a  NEU- 
RON, .-/,  or  nerve  cell  with 
all  its  parts  —  dendrites, 
cell  body,  and  axon  ;  B,  a 
portion  of  a  white  fiber 
highly  magnified.    (Jegi.) 


municatc  with  every  other  sub- 
scriber, would  need  one  thousand 
wires  running  into  his  house ;  all 
together,  there  would  have  to  be 
several  hundred  thousand  (to  be 
exact,  499,500)  wires.  With  a  cen- 
tral office  only  one  thousand  are 
needed.  As  a  telephone  system 
has  central  offices,  so  the  nervous 
system  has  nerve  centers.  Nerve 
centers  contain  nerve  cells.  Al- 
though there  are  some  subordinate 
nerve  centers  in  the  spinal  cord, 
the  greatest  collection  of  nerve 
centers  in  our  bodies  is  in  the  skull, 
and  is  called  the  brain.  Fishes 
were  the  lowest  animals  studied  in 
animal  biology  found  to  possess  a 
true  brain. 

The  nervous  system,  unlike  a 
telephone  system,  has  other  duties 
besides  allowing  communication. 
It  enables  us  to  think,  and,  after 
reflection,  to  will  and  to  act  by  con- 
trolling the  various  cfrgans. 

The  Units  of  which  the  Nervous 
System  is  Constructed.  —  A  nerve 
cell  with  all  its  branches,  or  fibers, 
is  called  a  neuron  (see  Fig.  103); 
some  neuron  branches  are  several 
feet  long.  Neurons  are  the  units 
that  compose  the  nervous  system. 
The    living    substance    in    cells    is 


THE  NERVOUS  SYSTEM 


II9 


Fig.  104.  —  Large  Nerve  Trunk, 
such  as  supplies  the  muscles. 
Cross-section  (magnified  6  diam- 
eters), showing  bundles  of  nerve 
fibers.     (Peabody.) 


called  protoplasm.     The  protoplasm  in  nerve  cells  possesses 

the  most  marvelous  and  varied  powers  of  any  known  sub- 
stance, for  the  nerve  cells  are 

the  seat  of  the  mind. 

Nerve   Cells  and  Fibers.  — 

The  many  branches  of  nerve 

cells    make    them    the    most 

remarkable   of    all    cells    for 

irregularity  in   shape.     Since 

the  protoplasm  of  the  cell  con- 
tinues   into    the  fibers,    it    is 

plainly  wrong  to  consider  the 

nerve  cell  as  something  apart 

from    its    fibers.     It   is  not  a 

complete   cell   without  them. 

A  cell  usually  has  many  short 

branches    called    dendrons  or 

dendrites  (see  Fig.  103)  for  communicating 
with  near-by  cells,  and  one  long  branch 
called  an  axon  (Fig.  103)  for  communicat- 
ing with  distant  parts.  The  axons  form 
the  fibers  that  go  to  the  skin,  muscles, 
and  other  organs. 

A    Nerve. — These    long    branches,    or 

axons,  of  nerve  cells  go  all  over  the  body 

and  are  often  bound  together  into  visible 

jfijjj    cords  called  nerves,  or  nerve  trunks  (Fig. 

104). 

White   and   Gray   Fibers  (Fig.    105).  — 
Some    fibers    have    a   fatty   covering    sur- 

FlG.  105.  —  c,  a  white  j       s  a 

fiber  with  its  fatty  rounding  the  thread  of  protoplasm ;   they 
sheath  (dark) ;  d,  are  w}-,jte  an(j  glistening,  and  are  called 

two     gray     fibers 

(without  sheath),    white  fibers.    Others  are  without  this  fatty 


ill 


120 


HUMAN  BIOLOGY 


covering,  and  are  called  gray  fibers.  Both  kinds  of  fibers 
have  connective  tissue  on  the  outside  to  strengthen  them. 
If  we  let  a  lead  pencil  represent  a  white  fiber,  the  lead 
corresponds  to  the  axis  of  protoplasm  ;  the  wood  corre- 
sponds to  the  white,  shiny  fat  that  surrounds  it ;  and  the 
varnish  corresponds  to  connective  tissue  on  the  surface 
of  the  fiber.  A  number  of  white  fibers  together  makes 
a  white  mass  that  is  called  white  matter.  The  axis  of  a 
white  fiber,  of  course,  is  not  white.  A  mass  of  cells  or  of 
gray  fibers  is  called  gray  matte)'.  The  oxidation  of  the 
gray  matter,  or  protoplasm,  in  neurons  gives  rise  to  nerve 
energy. 

Feeling  Cells  and  Working  Cells.  —  Nerve  cells  are 
divided  into  two  classes  :  sensory  cells,  which  feel  or  receive 
impressions ;  and  motor  cells,  which  send  out  impressions 
to  the  working  organs.  Those  fibers  which  carry  impres- 
sions to  the  receiving  cells  are  called  sensory  fibers  ;  those 
which  carry  impulses  from  the  cells  to  the  working  organs 
are  called  motor  fibers. 

Ganglia  and  Nerve  Centers.  —  Nerve  cells  are  not  scat- 
tered uniformly  in  nervous  tissue,  but  are  gathered  into 
groups.  A  group  of  nerve  cells  is  called  a 
ganglion  (Fig.  106).  One  or  more  ganglia 
having  a  single  function,  such  as  to  control 
the  muscles  of  breathing,  form  what  is  called 
a  nerve  center.  The  brain  consists  of  a 
number  of  nerve  centers  with  their  connect- 
ing fibers. 

Gross  Structure  of  the  Spinal  Cord.  —  The 

nerve  fibers  from  nearly  all  over  the  body 

lead  to  cells  situated  in  a  large  cord  in  the  spinal  column 

called  the  spinal  cord.     The  spinal  cord  is  separated  by 

a  deep  fissure  almost  into   halves  (Fig.    1 07).     The  cells 


Fig.  106. —  A 
Ganglion. 


THE  XER VOL'S  SYSTEM 


121 


Fig.  107.  — Cross-section  of 
Spinal  Cord,  showing  area 
of  gray  matter  (dark). 


are  situated  in  the  central  portion  of  each  half,  and  the 

two  masses  of  gray  matter  thus  formed  are  connected  by  a 

narrow  isthmus  of  gray  matter. 

The    outer    part    of    the    cord 

consists  chiefly  of  white  fibers. 

The  white  matter  is  thus  on  the 

outside    of  the  cord  (Fig.    107). 

The  brain,  unlike  the  cord,  has 

the  gray  matter  on  the  outside 

and  the  white  matter  on  the  in- 
side.    For  microscopic  study  of 

the  spinal  cord,  see  Fig.  108. 

The  Work  of  the  Spinal  Cord. — There  are  two  functions 

of  the  cord  :    reflex   action  and  transmission  of  impulses 

from  the  body  to  the  brain. 
Reflex  action  is  action  that 
takes  place  without  the  aid 
of  the  will. 

Reflex  action  never  begins 
in  the  cord,  but  at  the  outer 
end  of  a  sensory  fiber,  usu- 
ally located  in  the  skin. 
The  impression  goes  to  the 
cord  along  a  sensory  fiber. 
It  is  received  in  a  sensory 
cell  and  transferred  by  den- 
drons  to  a  motor  cell  which 
sends  back  an  impulse  along 
a  motor  fiber  to  a  muscle  ; 
the  muscle  contracts  and 
the  action  is  complete.     At 

least  two  nerve  cells  are  necessary  for  reflex  action.     The 

actions  of  the  lowest  animals  are  almost  entirely  reflex. 


Fig.  108.  —  Section  of  Spinal 
CORD,  showing  nerve  cells  (large 
black  spots)  with  their  branches 
(black  dots  and  lines).  Five 
bundles  of  nerve  fibers  are  shown 
near  upper  margin.     (Peabody.) 


I  22 


1/ I'M  AX  BIOLOGY 


Reflex  Action,  Consciousness,  and  Will.  — Usually  not  all 
of  the  force  of  the  impulse  is  transferred  to  the  motor  cell. 
The  sensory  cell  by  means  of  another  of  its  many  branches 
may  transfer  part  of  the  impulse  to  a  cell  which  sends  it  to 
the  brain.  Hence  a  reflex  act  is  not  necessarily  an  uncon- 
scious one.  If  you  unintentionally  touch  the  hand  to  a 
hot  stove  pipe,  you  may  be  conscious  of  the  pain  and  the 
involuntary  jerking  away  of  the  hand  at  the  same  time. 
Reflex  Action  and  the  Will.  —  The  will  may  inhibit,  or 
prevent,  an  expected  reflex  act.  Yet  many  reflex  acts 
occur  in  spite  of  the  effort  of  the  will  to 
prevent  them.  One  cannot  always  keep 
from  closing  the  eyes  before  a  threatened 
blow  even  if  from  the  other  side  of  a  plate 
glass  window,  and  it  is  known  there  is  no 
danger.  Sneezing  is  a  reflex  act  and  can- 
not always  be  prevented.  The  forming  of 
saliva  and  other  secretions  are  reflex  acts. 
Reflex  acts  are  quicker  than  voluntary  acts. 
An  eighth  of  a  second  is  about  the  time 
required  for  a  person  to  press  an  electric 
button  after  seeing  a  signal ;  a  reflex  act 
may  occur  in  a  shorter  time. 

The  Brain  consists  of  Three  Chief  Parts. 
—  ( i )  There  is  an  enlargement  at  the  top 
of  the  spinal  cord  called  the  medulla,  or 
the  medulla  oblongata.  It  may  be  re- 
garded as  the  part  of  the  spinal  cord 
jwfuv  -  within  the  skull  (see  Figs.  109,  no,  114). 
7jS\\\  (2)  Above  the  medulla  is  the  cerebellum, 

1  or  little  brain.     (3)  The  cerebrum,  or  large 

fig.  109. -brain    brai      fin     a]1     h     gkull  t  th     small 

AND   MMNAL  '  r 

Cord.  part   occupied  by  the   medulla  and    cere- 


THE  NERVOUS   SYSTEM 


123 


bellum.  The  cerebrum  covers  the  cerebellum.  (Fig. 
no.)     Is  this   true  of   the   monkey's   brain?     (See    Fig. 

H3-) 

The  work  of  the  medulla  is  chiefly  to  control  the  vital 
functions  (see  Figs,  no,  114).  Here  are  located  the 
centers  for  regulating  the 
breathing,  the  heart  beat,  the 
size  of  the  blood  vessels  (thus 
regulating  nutrition),  and  also 
the  less  important  centers 
that  control  swallowing,  secre- 
tion of  saliva,  and  vomiting. 
The  center  for  breathing  is 
sometimes    called     the     vital     fig.  no.  — the  brain  (cerebrum, 

cerebellum,  medulla). 

knot,    because    although    the 

cerebrum  and  cerebellum  may  be  removed  from  an  animal 
without  causing  immediate  death,  the  slightest  injury 
to  the  vital  knot  kills  the  animal  at  once.     In  cases  of 

hanging,  death  is  caused  by 
injury  to  this  center. 

Automatic  Action.  —  The 
center  called  the  vital  knot 
is  said  to  regulate  the 
breathing  automatically,  not 
reflexly.  Reflex  acts  start 
in  the  skin ;  automatic  acts 
start  in  the  interior  of  the 
body.  The  condition  of  the  blood  regulates  the  breathing 
automatically  during  sleep,  and  partly  regulates  it  during 
waking.  If  too  much  carbon  dioxid  accumulates  in  the 
blood  this  excites  the  vital  knot,  which  sends  out  stronger 
impulses  to  the  respiratory  muscles.  Deeper  breathing 
follows,  which  purifies  the  blood,  and  the  breathing  is  then 


Fig.  in.  —  Association  Fibers,  con- 
necting cells  within  the  cerebrum. 
(Jegi.) 


124 


//I'M. IX  BIOLOGY 


Fig.  112. —  Sensory  and  Motor 
Fibers.     (Jegi.) 


shallow   or  slow   until   carbon   dioxid    accumulates    again. 
The  Four  Kinds  of  Nerve  Action  and  the  Centers  that  con- 
trol them.  —  The  cord  controls    chiefly    reflex   action ;  the 
medulla  controls  chiefly  automatic  action  ;  the  cerebellum 

controls  chiefly  coordinate,  or 
harmonizing,  action ;  the  cere- 
brum controls  the  purely  vol- 
untary acts,  for  it  is  the  seat 
of  consciousness  and  thought. 
The  medulla,  like  the  cord, 
has  the  gray  matter  on  the 
inside  (Fig.  109). 

Structure  of  the  Cere- 
bellum. —  The  cerebellum, 
like  the  cerebrum,  has  the 
gray  matter  or  cells  on  the  outside.  The  gray  matter  is 
folded  into  furrows  that  are  not  nearly  so  winding  as  the 
folds  in  the  cerebrum  (see  Fig.  115).  The  fibers  going 
to  the  surface 
cells  have  a 
branched  arrange- 
ment called  the 
arbor  vita,  or  tree 
of  life,  which  is 
shown  where  the 
cerebellum  is  cut. 
The  cerebellum, 
like  the  cere- 
brum, is  deeply 
cleft  and  thus  divided  into  halves,  called  hemispheres, 
connected  by  a  band  of  white  matter. 

The  work  of  the  cerebellum  is  to  aid  the  cerebrum  in 
controlling  the  muscles.     //  coordinates  the  muscular  move- 


Fig.  113.  —  Brain  of  a  Monkey.     Numerals 
show  location  of  motor  centers.     (See  Fig.  115.) 


THE  NERVOUS  SYSTEM 


125 


ments  ;  that  is,  it  makes  the 
muscles  act  at  the  right 
time  and  with  due  force  in 
complex  acts,  such  as  stand- 
ing, walking,  talking.  A 
man  could  strike  just  as 
hard  without  the  action  of 
the  cerebellum,  but  he  would 
not  be  likely  to  hit  what  he 
aimed  at.  A  drunken 
man  staggers  and  fails  to 
control  the  muscles  in  walk- 
ing because  the  alcohol  has 
caused  the  blood  to  collect 
and  congest  around  the 
cerebellum  and  press  upon 
it.  One  whose  cerebellum 
has  been  injured  by  accident 


Cerebri 


Fig.  114.  --The  Lobes  of  the  Right 
Side  of  Brain  and  their  functions. 
(Jegi.) 

The  speech  center  is  true  only  for  left-handed 
persons.     Medulla  is  marked  "  Bulb." 


staggers  like  a  drunken  man. 
Coverings  of 
the  Brain.  —  Lin- 
ing the  skull  and 
covering  the  cere- 
brum are  found 
two  membranes 
which  inclose  a 
lymph-like  fluid. 
Thus  a  kind  of 
water  bed'\%  made 
which  surrounds 
the  soft  and  deli- 
cate cerebrum 
Fig.  115.  — Motor  and  Sensory  Areas  of  Left 

Hemisphere.     Speech- center  marked  "  Lips."  anc^      protects      It 

In  what  region  are  the  motor  centers?     The  sensory  centers?        I  TO  Ul       J  a  T  S.         i\ 


126  HUMAN  BIOLOGY 

membraneous  net,  or  mesh  work,  of  blood  vessels  covers 
the  cerebrum  and  plentifully  supplies  it  with  blood. 

Structure  of  the  Cerebrum.  —  The  gray  matter,  or  cell 
mass  of  the  cerebrum,  forms  a  surface  layer,  called  the 
cortex  ("  bark  "),  about  one  eighth  of  an  inch  thick.  This 
gray  layer  is  deeply  folded,  the  folds,  or  convolutions,  being 
separated  by  deep  furrows,  some  of  them  an  inch  deep 
(see  Fig.  no).  Thus  the  area  of  the  surface  layer  is 
increased  to  several  times  what  it  would  be  if  smooth. 
Intelligence  increases  with  increase  in  the  number  and 
depth  of  the  convolutions.  The  greater  part  of  the  cere- 
brum is  white  matter.  This  consists  largely  of  associa- 
tion -A fibers  (Fig.  in)  ivhich  connect  the  cells  in  the  gray 
matter  with  each  other  and  with  important  interior  ganglia 
at  the  base  of  the  cerebrum  (Fig.  112).  These  basal 
ganglia  are  the  largest  parts  of  the  brains  of  the  lower 
vertebrates  (Animal  Biology,  Figs.  222,  259).  Why  do 
these  animals  not  need  large  cerebrums  ?  The  human 
cerebrum  comprises  nearly  seven  eighths  of  the  weight 
of  the  brain.  A  deep  fissure  divides  it  into  the  right  and 
left  cerebral  hemispheres.  A  band  of  white  matter  con- 
nects the  hemispheres. 

Functions  of  the  Cerebrum.  —  The  cerebrum  is  the  seat  of 
consciousness  and  thought,  and  of  all  activity  controlled  by 
the  will.  It  also  directs  the  work  of  the  lower  nerve  centers 
in  the  spinal  cord,  medulla,  and  cerebellum. 

It  receives  sensory  messages  from  all  parts  of  the  skin 
and  through  the  special  senses.  It  sends  out  motor  mes- 
sages to  all  the  voluntary  muscles,  and  more  indirectly 
to  the  involuntary  muscles.  The  cerebral  fibers  are  of 
three  kinds  :  sensory,  associational  (connecting  cells  in  cere- 
brum), and  motor  (Figs.  111,112).  It  is  estimated  that  the 
cerebrum  alone  contains  9,200,000,000  cells. 


THE  NERVOUS  SYSTEM  \2J 

Spinal  and  Cranial  Nerves.  —  The  nerves  from  the  spinal  cord  go 
out  through  notches  between  the  vertebrae.  Since  there  are  tliirty-one 
pairs  of  spinal  nerves  (Fig.  109)  and  only  twenty-four  vertebras,  some 
of  the  nerves  go  out  through  holes  in  the  sacrum.  The  cranial  nerves 
(to  eyes,  ears,  tongue,  nose,  face,  etc.)  leave  the  brain  through  holes  in 
the  cranium,  or  skull.     There  are  twelve  pairs  of  them. 

Relation  of  the  Cerebrum  to  the  Lower  Centers.  —  As  already  stated, 
nerve  activities  are  of  four  kinds,  —  reflex,  automatic,  coordinate,  and 
voluntary.  A  manufactory  has  more  complex  work  than  a  shop.  A 
man  with  a  shop  may  enlarge  it  into  a  factory  and  leave  trained  assist- 
ants in  charge  of  the  different  shops,  keeping  only  the  general  man- 
agement for  himself.  If  he  should  cease  to  control  his  assistants 
entirely,  the  work  of  the  factory  would  soon  be  in  disorder.  If  the 
manager  should  try  to  direct  everything,  he  would  become  exhausted. 
So  the  cerebrum,  the  seat  of  the  will  and  the  reason,  leaves  the  reflex 
centers  in  the  spinal  cord,  medulla,  and  cerebellum  to  do  most  of  the 
work.  If  the  mind  wishes  the  hand  to  move  and  grasp  the  hand  of 
a  friend,  the  motor  center  in  the  cerebrum  sends  a  message  to  the 
cerebellum;  and  if  the  cerebellum  has  been  well  trained,  the  act  is 
accurately  performed. 

A  less  imperfect  wisdom  than  that  of  the  mind  is  in  the  lower 
nerve  centers.  The  reason  and  will  control  the  lower  centers  through 
the  cerebrum,  but  the  control  is  very  limited.  It  is  well  that  this  is 
so,  not  only  for  the  relief  of  the  cerebrum,  but  for  the  safety  of  the 
body.  Can  you  change  the  rate  of  the  heart  beat  by  the  exercise  of 
the  will?  Can  you  blush  at  will,  or  prevent  the  flushing  of  the  capil- 
laries when  you  are  embarrassed,  or  when  you  go  close  to  a  hot  fire? 
It  is  impossible  for  a  person  to  commit  suicide  by  holding  the  breath. 
What  change  in  the  blood  would  soon  force  a  breath  to  be  taken? 
Repeat  the  two  examples  of  reflex  action  triumphing  over  the  will 
which  have  already  been  given.  We  shall  next  take  up  a  system  of 
nerves  almost  independent  of  the  will. 

The  ganglionic  or  sympathetic  portion  of  the  nervous 
system  controls  the  viscera  (vis'se-ra),  or  internal  organs, 
e.g.  peristalsis  of  food  tube,  tone  of  arteries.  The  nerves 
that  go  to  the  viscera  branch  off  from  the  spinal  nerves 
not  far  from  the  spinal  column,  and  enter  a  row  of  ganglia 
on  each  side  of  the  spine  (see  Fig.  115).  Each  ganglion 
is  connected  by  nerves  with  the  one  above  and  below  it, 
so  that  they  appear  like  two  knotted  cords  suspended  one 


128 


JIf.UA.V  BIOLOGY 


on  each  side  of  the  spinal  column  and  tied  together  below ; 
for  both  chains  of  ganglia  end  in  the  same  ganglion  in 
the  pelvis.  Some  of  the  fibers  from  the  spinal  cord  pass 
through  these  ganglia  on  their  way  to  the  viscera,  losing 
their  white  sheaths  in  the  ganglia  and  emerging  as  gray 
fibers.  The  spinal  cord  and  brain  with  the  fibers  which 
do  not  pass  through  the  double  chain  of  ganglia  are  called 

the  cere bro  -  spinal  system. 
The  double  chain  of  ganglia 
and  the  fibers  which  go 
through  them  are  called  the 
ganglionic  or  sympathetic 
system. 

Why  these  Nerves  are 
called  the  Sympathetic 
System.  —  These  nerves, 
after  leaving  the  double 
chain  of  ganglia,  form  many 
intricate  networks  of  ganglia 
and  fibers.  Each  network 
is  called  a  plexus  (Fig.  116). 
The  largest  of  the  plexuses 
is  just  back  of  the  stomach, 
and  is  called  the  solar  plexus. 
A  blow  upon  the  stomach 
may  paralyze  this  plexus 
The  plexuses  and  fibers  con- 
nect the  viscera  so  perfectly  that  one  organ  cannot  suffer 
without  the  others  changing  their  activity,  or  sympathising 
with  it.  An  overloaded  stomach  causes  the  heart  to 
beat  faster  and  send  it  more  blood  ;  a  loss  of  appetite 
usually  accompanies  illness  and  allows  the  stomach  to 
rest.     This   sympathy   is  necessary,   for   if    one  organ  is 


Fig.  116.  —  Diagram  of  Sympa- 
thetic System  showing  double 
chain  of  ganglia  ;  also  plexus  at 
heart  and  solar  plexus. 

and    cause    sudden   death. 


THE   NERVOUS   SYSTEM 


129 


diseased,  the  others  do  not  continue  to  work  and  tax 
the  strength  of  the  ailing  organ. 

How  the  Sympathetic  and  Cerebrospinal  Nerves  Differ.  — 
The    ganglionic    nerves   ( 1 )   contain    mostly  gray  fibers ; 

(2)  pass   through  ganglia  after   leaving  the   spinal   cord  ; 

(3)  control  the  unconscious  activities  of  the  body;  (4)  pass 
to  organs  which  contain  slow-acting  involuntary  muscles, 
not  to  sense  organs  and  quick-acting  voluntary  muscles; 
(5)  transmit  impulses  slowly  (about  20  ft.  instead  of  100 
ft.  per  second).  Crawfish  and  insects  have  hardly  more 
than  the  ganglionic  system  of  nerves  (Animal  Biology, 
Figs.  92,  132,  197). 

Examples  of  the  Supervisory  Functions  of  the  Sympa- 
thetic System.  —  Regulation  of  the  heart  beat  and  of  the 
size  of  the  blood  vessels  ;  secretion  of  sweat  glands ;  con- 
traction of  pupils  of  eyes  in  a  bright  light ;    peristalsis. 

Examples  of  Sympathetic  Nerve  Impulses  reaching  Con- 
sciousness. —  Pain  in  colic  and  cramps ;  "  heartburn " 
(pain  in  stomach  from  indigestion) ;  backache  (from 
nerves  in  organs  prolapsed  by  tight  clothing  pulling  upon 
their  attachments  at  spine) ;  hunger  ;  thirst. 

The  Mind  and  Health.  —  A  contented  or  peaceful  mind  is  indispen- 
sable to  soundest  health.  Worry  causes  difficult  breathing  with  bated 
breath.  Happiness  brings  full,  easy  breathing.  Biological  study  of 
physiology  shows  the  futility  of  making  health  a  care  or  anxiety,  and 
teaches  "no  meddling"  with  the  body,  whether  by  stimulating  it,  drug- 
ging it,  deforming  it,  overheating  it,  half  smothering  it  in  close  rooms, 
cultivating  artificial  instincts,  etc.  If  the  body  degenerates  through 
wrong  living,  and  disease  ensues,  a  new  way  of  living  is  needed,  not 
some  quick  and  wonderful  remedy.  The  new  life  will  renew  the  body 
and  nothing  else  can. 

Hygiene  of  the  Nervous  System 

Necessity  of  Food,  Fresh  Air,  and  Rest  for  Sound  Nerves. 
—  The  health  of  the  nerves  depends  upon  a  free  supply  of 

K 


i3o 


HUMAN  BIOLOGY 


pure,  nutritious  blood.  Nearly  one  fifth  of  the  blood  goes 
to  the  brain.  It  is  clear  that  the  brain  cannot  give  out 
energy  until  it  has  first  received  it ;  the  blood  supplies 
energy  to  the  brain.  The  blood  in  turn  receives  the  nour- 
ishment from  food  and  pure 
air.  A  rested  cell  is  full  of 
nourishment ;  a  tired  cell  is 
shriveled  (see  Fig.  117). 

Sleep.  —  During  waking 
hours  energy  is  used  up 
faster  than  it  is  stored  in 
the  cells,  and  protoplasm  is 
oxidized  faster  than  the 
cells  can  replace  it.  Dur- 
ing sleep  the  opposite  is 
true ;  repair  is  more  rapid 
than  waste.  During  sleep 
the  muscles  are  strength- 
ened, the  breathing  is  less, 
the  heart  beats  more  slowly, 
less  heat  is  produced,  diges- 
tion is  slower,  less  blood  goes  to  the  brain.  Why  is  it 
necessary  to  be  more  warmly  protected  by  clothing  or  bed 
covering  when  asleep  than  when  awake  ?  Above  all,  the 
nervous  system  has  an  opportunity  to  recuperate  from  the 
constant  activity  of  waking  hours.  The  eye  and  the  ear 
are  rested  by  darkness  and  silence.  Sleep  caused  by 
morphine  or  other  drug  is  not  normal  sleep  and  brings 
little  refreshment. 


Fig.  117.  — Effects  of  Fatigue  on 
Nerve  Cells. 

A,  resting  cell,  B,  fatigued  cell,  with  its 
body  and  nucleus  shrunken. 


Practical  Suggestions.  —  Sleep  is  deepest  during  the  second  hour 
after  going  to  sleep,  and  a  greater  shock  is  given  to  the  nervous  system 
by  waking  a  sleeper  during  that  hour  than  at  another  time.  An  alarm 
clock  is  a  very  unhealthful  device.     One  who  cannot  trust  to  nature 


THE  NERVOUS  SYSTEM  131 

even  to  awaken  has  great  presumption.  If  one  does  not  rise  promptly 
upon  waking  naturally,  the  instinct  to  awake  when  enough  sleep  has 
been  taken  will  be  lost,  and  the  habit  of  sleeping  too  much  will  be 
formed,  and  the  brain,  like  the  muscles,  will  become  weak  from 
inactivity.  Infants  sleep  most  of  the  time,  and  it  is  injurious  to  them  to 
be  waked.  Adults  usually  require  about  eight  hours  of  sleep.  There  is 
a  risk  in  going  to  sleep  in  a  warm  room,  for  the  bed  covering  which  is 
comfortable  then  may  not  be  enough  to  prevent  taking  cold  when  the 
fire  goes  out.  Sleep  usually  comes  more  promptly  to  one  who  goes  to 
bed  at  the  same  hour  each  night.  The  muscles  are  relaxed  in  sleep, 
and  relaxing  them  perfectly  upon  lying  down  and  breathing  slowly, 
tends  to  bring  sleep.  One  who  is  sleepless  usually  finds  that  he  is 
breathing  fast  and  is  holding  the  head  stiff  on  the  shoulders,  the  teeth 
clenched,  and  the  muscles  contracted,  even  though  he  is  lying  down. 
Excitement  and  worry  during  the  day.  but  especially  just  before  retiring, 
tend  to  produce  sleeplessness.  One  who  overworks  his  mind  by  too 
great  attention  to  business  is  inviting  ruin.  A  student  who  loses  sleep 
while  preparing  for  an  examination  will  probably  fail.  Rested  brain 
cells  and  pure  blood  are  needed  for  good  work. 

Rules  for  Preventing  Sleepiness.  —  ( 1 )  Do  not  sit  close  to  stove  or 
especially  a  fireplace  or  in  very  warm  room,  and  do  not  wear  very 
warm  clothing  in  the  house.  (2)  Let  in  fresh  air  freely.  (3)  Do  not 
sit  in  rocking  chair  nor  with  chest  flattened.  (4)  Make  the  last  meal  a 
very  light  one. 

Habits.  —  Our  habits  of  doing  and  thinking  and  feeling 
really  constitute  our  characters.  This  shows  the  impor- 
tance of  right  habits.  By  gradually  changing  our  habits 
we  can  strengthen  our  characters  and  form  them  somewhat 
as  we  wish.  When  a  muscle  contracts  in  a  certain  way, 
this  act  makes  it  easier  for  the  muscle  to  contract  in  that 
way  the  next  time  ;  thus  great  muscular  strength  may  be 
developed.  When  a  nerve  cell  acts,  the  circulation  around 
the  cell  is  increased,  the  fibers  develop  by  use,  and  the  act 
is  easier  the  next  time.  We  cannot  entirely  get  rid  of  our 
habits,  because  we  cannot  get  rid  of  our  brains. 

Healthy  fatigue  is  caused  by  the  accumulation  of  waste 
products  resulting  from  the  oxidation  of  substances  in 
nerve,  muscle,  and  gland  cells.     The  presence  of  waste  in 


132 


HUMAN  BIOLOGY 


the  tissues  affects  the  nerves.  We  are  rested  and  strong 
when  these  wastes  are  removed  and  the  tissues  are  sup- 
plied with  fresh  food  and  oxygen.  Work  causes  the  ac- 
cumulation of  carbon  dioxid,  which  is  nature  s  narcotic.1 
The  drowsy  feeling  that  ensues  is  more  pleasant  than  the 
drowsy  feeling  from  alcohol  or  opium.  Those  who  do 
not  employ  nature's  narcotic  but  free  themselves  of  it  by 
hurried,  anxious  breathing  become  restless  and  crave  arti- 
ficial narcotics. 

Fatigue  without  work  occurs  with  people  who  are  idle. 
The  oxidation  in  their  cells  is  not  complete,  and  poisonous 
products  of  the  incomplete  burning  result.  This  is  known 
as  self-poisoning  (auto-toxemia).  The  poisons  are  taken 
by  the  blood  to  the  nerves  and  brain,  and  give  a  tired  feel- 
ing as  effectually  as  does  hard  work ;  or  the  food  may  fer- 
ment   in    the    food 

.  'MIA   !___ 
PELVIC 


ANEM&dm 


EYE  37MW,..: 


OiSTWBANCES  Ofi 
AOS£,  EAR,  AND 
O£CAY£0  T££TH 


.-NEMGUS  EtHAVSmON 
'—■SPINAL  MITAm* 


tube  and  form  poi- 
sons which  increase 
the  tired  feeling. 
Such  persons  are 
usually  irritable, 
while  persons  who 
are  fatigued  by  use- 
ful labor  are  likely 
to  be  dull  and 
drowsy. 

Headaches     are 
caused    by  poisons 

in  the  blood  or  by  pressure  of  blood  congested  in  the  head. 

Like  all  other  pains  they  should  be  a  source  of  benefit  in 

1  It  has  been  found  that  it  is  injurious  to  rebreathe  expired  air  containing 
one  per  cent  of  carbon  dioxid,  but  a  far  greater  percentage  is  harmless  if  intro- 
duced into  fresh  air,  thus  indicating  that  the  injury  from  poor  ventilation 
comes  chiefly  from  the  "  crowd  poison,"  or  organic  particles  thrown  off. 


Fig.  118.  — The  Situation  of  Headaches 
with  reference  to  their  causes. 


THE  NERVOUS  SYSTEM  I  33 

that  they  show  us  ways  of  living  to  be  shunned  in  the 
future.  Many  persons,  however,  not  only  derive  no  profit 
from  a  headache,  but  by  unwise  efforts  to  cure  the  pain, 
bring  permanent  injury  to  themselves  in  addition  to  the 
suffering  of  the  headache. 

Bromides,  opium,  and  other  poisons  deaden  and  weaken 
the  nervous  system  while  preventing  the  headache  from 
being  felt.  Headache  powders,  phenacetin,  acetanelid,  an- 
tikamnia,  and  other  vile  poisons  made  from  coal  tar,  shock 
and  weaken  the  heart  and  reduce  the  vital  activities  so 
that  the  headache  is  no  longer  felt.  In  consequence  of 
shocks  from  repeated  doses  of  such  drugs,  the  heart  will 
not  work  so  well,  and  may  give  way  some  time  in  the 
future  when  an  effort  or  strain  makes  unusual  demands 
upon  it.  Their  use  has  made  heart  disease  more  preva- 
lent. The  liver  and  kidney  cells  and  the  white  corpuscles 
have  to  destroy  and  remove  the  drugs.  Many  people 
are  foolish  enough  to  injure  their  bodies  and  risk  death 
rather  than  suffer  pain  or  avoid  pain  by  prudent  living. 

Sick  headaches  are  foretold  by  a  dull  feeling,  sleepiness 
after  eating,  a  coated  tongue,  and  constipation.  It  would 
be  better  to  remove  the  undigested,  spoiled  food  from  the 
stomach  (four  glasses  of  water  will  cause  vomiting)  than 
to  take  a  drug.  At  the  first  indication  of  trouble,  ab- 
stain from  eating,  or  use  a  fruit  diet  for  twenty-four 
hours,  and  drink  water  freely.  This  will  enable  the 
body    to    dispose    of   the    excess    of    waste    matter. 

The  Highest  Living  Medical  Authority  on  Drugs. —  Dr. 
Osier,  formerly  of  Johns  Hopkins  University  and  now 
of  Oxford  University,  says : 

"  But  the  new  school  does  not  feel  itself  under  obligation  to  give  any 
medicines  whatever,  while  a  generation  ago  not  only  could  few  phy- 
sicians have  held  their  practice  unless  they  did,  but  few  would  have 


134  HUMAN  BIOLOGY 

thought  it  safe  <>r  scientific.  Of  course  there  are  still  many  cases  where 
the  patient  or  the  patient's  friends  must  he  humored  by  administering 
medicine,  or  alleged  medicine,  where  it  is  not  really  needed,  and  indeed 
often  where  the  buoyancy  of  mind,  which  is  the  real  curative  agent,  can 
only  be  created  by  making  him  wait  hopefully  for  the  expected  action 
lit  medicine;  aw\  some  physicians  still  cannot  unlearn  their  old  train- 
ing. But  the  change  is  great.  The  modern  treatment  of  disease 
relies  very  greatly  on  the  old  so-called  natural  methods,  diet  and  exer- 
cise, bathing  and  massage,  in  other  words  giving  the  natural  forces  the 
fullest  scope  by  easy  and  thorough  nutrition,  increased  flow  of  blood, 
and  removal  of  obstructions  to  the  excretory  systems  or  the  circulation 
in  the  tissues.  One  notable  example  is  typhoid  fever.  At  the  outset  of 
the  nineteenth  century  it  was  treated  with  "  remedies"  of  the  extremest 
violence, —  bleeding  and  blistering,  vomiting  and  purging,  antimony  and 
calomel,  and  other  heroic  remedies.  Now  the  patient  is  bathed  and 
nursed  and  carefully  tended,  but  rarely  given  medicine.  This  is  there- 
suit  partly  of  the  remarkable  experiments  of  the  Paris  and  Vienna 
schools  into  the  action  of  drugs  which  have  shaken  the  stoutest  faiths; 
and  partly  of  the  constant  and  reproachful  object  lesson  of  homeopathy. 
No  regular  physician  would  ever  admit  that  the  homeopathic  "  infini- 
tesimals "  could  do  any  good  as  direct  curative  agents ;  and  yet  it  was 
perfectly  certain  that  homeopaths  lost  no  more  of  their  patients  than 
others.  There  was  but  one  conclusion  to  draw,  that  most  drugs  had 
no  effect  whatever  on  the  diseases  for  which  they  were  administered." 
—  u  Encyclopaedia  Americana."'  Vol.  X.     (Munn  &  Co.,  New  York.) 

Applying  Hygienic  Tests  Systematically.  —  The  cause  of  ill  health 
(e.g.  a  headache)  should  be  sought  with  system  and  thoroughness,  ap- 
plying the  tests  in  rotation  to  every  function  of  the  body :  Lungs.  Is 
the  air  habitually  breathed  fresh  and  free  from  dust?  Is  the  body  held 
up,  and  is  the  chest  or  waist  cramped  by  clothing?  Muscles.  Is 
enough  physical  exertion  made  to  cause  deep  breaths  to  be  drawn? 
Food.  Is  it  simple,  digestible,  and  eaten  properly?  Drink.  Is  the 
water  pure?  Cleanliness,  Work  and  Rest,  Clothing,  Ventilation,  and 
Mental  State  may  be  inquired  into  until  the  source  of  trouble  is  found 
and  the  cause  of  ill  health  removed.  To  give  drugs  and  leave  the  cause  of 
ill  health  untouched,  is  to  fail.  There  are  signs  of  coming  weakness  or 
illness  which,  if  heeded  and  the  ways  of  living  improved,  will  usually 
prevent  illness.  Among  these  signs  are  headaches,  paleness,  sensi- 
tiveness to  cold,  heavy  feeling  or  pain  after  meals,  constipation.  Huxley 
says  that  young  people  should  so  learn  physiology  and  so  understand 
their  bodies  that  they  will  heed  the  first  sign  of  nature's  displeasure, 
and  not  watt  for  a  box  on  the  ear. 


THE  NERVOUS  SYSTEM  I  35 

Nervous  Children.  —  A  report  on  the  health  of  the  school  children  in 
one  of  our  large  cities  shows  that  one  third  of  the  children  in  those  schools 
have  some  disorder  of  the  nerves.  Nervousness  (weakened  control  of 
the  nerves)  may  show  itself  by  sluggishness  of  mind,  great  irritability 
of  temper,  frequent  spells  of  tlie  "  blues,"  or  by  involuntary  movements 
of a  jerky  or  fidgety  kind.  Sound  development  of  city  children's  nerves 
is  hindered  because  of  the  constant  noise  in  cities  both  day  and  night ; 
by  shortening  of  the  hours  of  sleep  ;  by  excessive  use  of  sugar  for  food  ; 
by  living  much  among  people  with  no  chance  to  be  alone  and  let  the 
nerves  rest,  and  among  boys  by  the  use  of  cigarettes. 

How  to  Prevent  the  School  from  injuring  Children.  — 

(1)  Ventilation  is  of  first  importance.  Breathing  the 
breath  of  fifty  other  children  does  far  more  harm  than 
overstudy.  (2)  The  time  devoted  to  zvork  should  not  be 
long,  especially  in  the  lower  grades  (no  study  out  of 
school).  (3)  The  work  should  be  diversified ;  not  only 
printed  words,  but  pictures,  natural  objects,  and  the  out- 
door world  should  be  studied.  (4)  The  teacher  and  parent 
should  see  that  the  habitual  poise  of  the  child  is  favorable 
to  health.  (5)  The  children  should  be  encouraged  to  play. 
Running  games  at  recess  are  of  the  greatest  value,  and 
are  as  indispensable  to  the  health  of  a  boy  or  girl  as  of  a 
colt.  (6)  Physical  exercise  should  be  provided  at  short 
intervals  between  lessons,  especially  stretching  exercises 
and  movements  that  straighten  the  spine  and  hips  and  ele- 
vate the  chest. 

The  Effect  of  Alcohol  upon  Nerve  Function.  —  In  attack- 
ing the  nerve  centers,  alcohol  begins  with  the  cerebrum, 
the  highest,  and  proceeds  toward  the  lowest.  Hence  as  a 
man  becomes  drunk  he  first  talks  foolishly  (cerebrum 
affected),  then  he  staggers  (cerebellum  affected),  and  he 
finally  goes  to  sleep  and  breathes  very  hard  (medulla 
affected)  in  a  drunken  stupor.  It  rarely  happens  that  the 
breathing  center  is  completely  disabled  and  the  man  dies 
from  the  strong  poison.     The   greatest  evil  of  alcohol  is 


136  HUMAN  BIOLOGY 

seen  in  the  case  of  steady  drinking.  This  gradually  de- 
troys  the  soundness  of  the  nervous  system  and  weakens 
self-control.  The  tendency  with  nearly  all  drinkers  is  to 
increase  the  amount  taken. 

Not  Total  Abstainers,  but  the  Advocates  of  Universal 
Moderation  are  the  Visionaries. — The  evil  results  from 
alcohol  are  so  great  as  to  be  almost  incredible.  The 
plainest  statements  of  its  effects  are  sometimes  denounced 
as  unscientific  by  persons  prejudiced  in  its  favor.  A  part 
of  the  two  billion  dollars  annually  paid  for  liquors  is  used 
in  influencing  public  opinion  through  the  press. 

Practical  Questions.  —  1.  Why  does  travel  often  cure  a  sick 
person  when  all  else  fails  ?  2.  Why  is  working  more  healthful  than 
"taking  exercise1"?  (p.  47.)  3.  Is  it  better  for  children  to  play  or  to 
take  exercise  ?  4.  Why  can  one  walk  and  carry  on  a  conversation  at 
the  same  time  ?  (p.  127.)  5.  How  does  indigestion  cause  a  headache? 
(P-  l33-)  ^-  Does  perfectly  comfortable  clothing  from  head  to  foot 
help  to  make  one  at  ease  in  company  ?  Does  uncomfortable  clothing 
tend  to  make  one  awkward  ?  7.  Why  is  it  as  important  to  have  the 
shoes  and  clothes  perfectly  comfortable  when  going  out  as  when  stay- 
ing at  home  ?  8.  When  one's  ringer  is  cut,  where  is  the  pain  ? 
9.  In  what  two  ways  may  opening  a  window  when  a  student  is  becom- 
ing dull  and  drowsy  at  his  books  enable  him  to  wake  up  and  study  with 
ease?  10.  What  kinds  of  cells  shrivel  like  a  baked  apple  when  they 
become  fatigued?  (Fig.  117.)  11.  A  nerve  or  nerve  fiber  can  hardly 
become  tired  or  fatigued,  for  the  nerve  cell  supplies  the  energy.  What 
do  we  mean  when  we  say  the  nerves  are  worn  out?  (Fig.  117.) 
12.  Why  do  you  throw  cold  water  upon  a  fainting  person  ?  13.  Why  does 
constant,  moderate  drinking  undermine  the  health  more  than  occasional 
intoxication  ?  14.  Why  does  stoppage  of  the  circulation  cause  one  to 
faint?  (See  Chap.  VI.)  15.  Why  is  grazing  the  skin  often  more  pain- 
ful than  cutting  it  ?  (Colored  Fig.  1.)  16.  Why  do  the  lower  ani- 
mals always  act  upon  sudden  impulse  ?  What  part  of  the  brain  enables 
man  to  retain  sensations  and  not  act  upon  them  until  later  ?  17.  Does 
"  nervousness  "  more  probably  indicate  a  bright  mind  or  a  high  temper  ? 

18.  What  is  the  effect  of  a  cold  bath  upon  the  nerves  ?     (Chap.  II.) 

19.  Did  you  ever  know  a  cigarette  smoker  whose  hand  trembled  ? 

20.  Need  there  be  any  fear  of  a  sobbing  child  holding  its  breath  until 
it  dies  ?     21.   Why  is  muscle  tone  greater  in  cold  weather  ? 

\ 


THE  NERVOUS  SYSTEM 


137 


The  True  Function  of  Stimulants.  —  One  whose  heart 
has  nearly  given  out  because  of  exposure  to  severe  weather 
may  be  temporarily  revived  by  alcohol.  It  ivill  not  be  wise 
to  do  so  unless  it  is  certain  that  a  warm  fire  and  protection 
zvill  be  reached  before  the  reaction  comes.  Much  less  would 
be  necessary  to  revive  an  abstainer  than  a  drunkard.  Ha- 
bitually disturbing  the  body  with  stimulants  makes  them 
ineffective  in  a  time  of  emergency.  A  cup  of  coffee  will 
not  keep  a  watcher  awake  if  he  is  used  to  coffee. 

Definitions  :  Stimulant,  Narcotic.  Poison.  —  A  stimulant 
is  anything  that  excites  the  body  to  activity,  but  is  of  no  help 
or  of  insignificant  help,  in  replacing  the  strength  used  up. 

A  narcotic  is  anything  that  deadens  or  dulls  the  nervous 
system.     It  comes  from  a  word  meaning  "  to  benumb." 

Poisons  are  active  substances,  which,  taken  in  quantities, 
as  man  takes  food,  destroy  life ;  in  smaller  quantities  they 
injure  the  body  and  may  destroy  life.  Alcohol  is  a  poison. 
Wine,  beer,  whisky,  contain  varying  quantities  of  it. 

The  Narcotic  and  Stimulant  Effects  of  Poisons.  —  Ex- 
amples of  poisons  are  alcohol,  nicotin,  opium,  arsenic, 
strychnin.  Poisons  excite  the  body  when  taken  in  small 
doses,  while  in  large  doses  they  produce  paralysis  and 
death.  The  irritating  or  stimulating  effect  is  due  to  de- 
rangement of  the  functions  or  to  the  efforts  of  the  cells  to 
free  the  body  of  the  destructive  substance.  The  narcotic 
effect  is  due  to  the  poison  having  so  benumbed  the  nerves 
and  injured  the  cells  that  their  activities  cease,  or  become 
less  for  a  time.  You  readily  see  how  the  same  poison  can 
be  both  a  stimulant  and  a  narcotic :  the  stimulating  effect 
ahvays  comes  first,  followed  by  the  stupefying  effect.  If  the 
dose  is  very  small,  the  stimulating  effect  will  last  longer; 
if  it  is  large,  the  narcotic  effect  is  greater  and  felt  more 
quickly.     A  habit  of  using  stimulants  is  an  invariable  sign 


138  HUMAN  BIOLOGY 

of  weakness.  The  first  dose  of  morphine  or  cocaine  may 
be  the  first  step  in  a  lifelong  blight  of  strength  and  happi- 
ness. If  physicians  whose  treatment  of  a  case  results  in 
leaving  a  patient  with  a  drug  or  alcohol  habit  were  sued 
for  malpractice,  they  would  be  less  reckless.  The  annual 
consumption  of  morphine  is  estimated  at  twenty-seven 
grains  per  capita  in  China,  and  fifty  grains  in  the  United 
States. 

Reaction. —  This  is  the  depressed  and  exhausted  condition 
that  comes  on  after  a  period  of  unnatural  activity.  It  fol- 
lows the  exciting  effects  of  a  stimulant. 

Natural  Stimulants.  —  If  there  were  nothing  to  arouse 
activity,  life  would  be  impossible.  A  cold  wind  is  a 
natural  stimulant.  The  activity  aroused  by  a  cold  wind  is 
just  enough  to  help  the  body  withstand  the  cold ;  artificial 
stimulants  cause  an  expenditure  having  no  relation  to  the 
needs  of 'the  body.  Hence  there  is  a  great  waste  of  energy. 
Feelings  may  stimulate,  as  love  for  his  family  may  stimu- 
late a  man  to  labor.  The  desire  for  knowledge  may  stimu- 
late a  boy  to  study.  Hunger  may  stimulate  a  man  to  eat. 
Hunger  is  a  natural  stimulant,  and  is  not  likely  to  make 
him  eat  to  excess ;  tea,  coffee,  pepper,  etc.,  arouse  a  false 
appetite.  These  things  are  used  chiefly  for  their  stimu- 
lant effect,  for  they  contain  little  or  no  nourishment.  We 
will  now  study  about  artificial  stimulants.  Such  stimulants 
ahvays  cause  an  unregulated  and  unhealthy  action,  and  are 
ahuays  followed  by  reaction. 

How  much  Strength  is  stored  in  the  Body?  —  Dr.  Tanner 
of  Minnesota  believed  that  most  people  eat  too  much. 
Another  physician  said  that  no  human  being  could  go  forty 
days  without  food.  Dr.  Tanner  made  the  experiment. 
He  lost  thirty-six  pounds  in  weight,  but  he  weighed  T21J 
pounds  and  had  considerable  strength  at  the  end  of  the 


THE  NERVOUS  SYSTEM  1 39 

forty  days.  The  first  thing  he  ate  at  the  close  of  his  fast 
was  the  juice  of  a  ripe  watermelon. 

Once  some  miners  were  shut  in  by  the  caving  of  a  part 
of  a  mine.  But,  unlike  the  case  just  described,  they  were 
without  water  as  well  as  food.  When,  by  digging,  the 
rescuers  reached  them  seven  days  after,  several  were  still 
found  alive,  although  most  of  them  had  died.  The  miners, 
no  doubt,  had  nourishment  in  their  bodies  for  some  weeks 
more  of  life,  but  the  body  lacked  water  to  dissolve  it  and 
bring  it  within  the  reach  of  the  cells  most  needing  it. 

A  Stupendous  Fact.  —  These  incidents  show  how  wisely 
the  body  is  made,  and  prove  that  the  cells  store  up  nourish- 
ment for  weeks  ahead.  The  large  amount  of  nourishment 
stored  in  the  human  body  is  one  of  the  most  striking  and 
important  facts  with  which  the  science  of  physiology  has 
to  deal,  and  it  should  be  borne  in  mind,  or  we  may  make 
great  mistakes  about  some  very  simple  matters  and  espe- 
cially in  regard  to  the  effects  of  stimulants. 

Foolish  Rashness.  —  Did  you  ever  get  so  tired  that  you 
had  to  give  up  and  stop,  however  much  you  would  have 
liked  to  continue  at  work  or  play  ?  To  rest  was  the  wise 
thing  to  do.  Because  you  know  there  is  much  energy 
stored  in  the  body,  this  need  not  tempt  you  to  go  on 
until  you  almost  break  down.  Probably  you  know  people 
who  are  conceited  about  their  bodies  and  say  they  are  "made 
of  cast  iron  "  ;  that  nothing  can  hurt  them.  Such  conceit 
will  be  almost  sure  to  get  its  possessor  into  trouble. 

How  a  Safeguard  may  be  broken  down.  —  It  is  a  very 
wise  arrangement  that,  under  ordinary  conditions,  we  can- 
not get  at  the  surplus  energy  we  have.  Carbon  dioxid  and 
other  wastes  accumulate  in  the  tissues  and  paralyze  the 
nerves.  Fatigue  and  other  feelings  compel  us  to  be  provi- 
dent, as  it  were ;  yet  stimulants  and  narcotics,  by  irritating 


140  HUMAN  BIOLOGY 

the  nerve  cells,  arouse  them  and  cause  us  to  expend  some 
of  this  reserve  energy.  Thus  man  is  enabled  to  get  at 
this  precious  store  which  he  should  save  for  emergencies, 
when  he  is  sick  and  cannot  digest  food,  or  when  he  is 
making  some  mighty  effort.  A  weak,  ill  man  who  has 
eaten  very  little  for  weeks,  when  delirious  is  sometimes  so 
powerful  that  it  takes  several  strong  men  to  hold  him  in 
bed.  But  the  delirious  mania  often  uses  up  the  little 
energy  left,  and  costs  the  man  his  life. 

The  only  source  of  energy  for  man's  body  is  the  union 
of  food  and  oxygen  ;  he  must  get  his  energy  from  the 
same  source  that  the  engine  does ;  and  this  is  from  his 
food,  which  serves  as  fuel,  and  the  oxygen  which  burns  it. 
If  one  has  been  working  hard  preparing  for  examinations, 
or  gathering  hay,  or  in  attending  to  some  important  busi- 
ness, or  has  been  under  the  excitement  of  some  pleasure 
trip,  and  feels  "  blue"  and  worn  out,  then  let  Jiim  bear  the 
result  like  a  man,  or  like  a  true  boy  or  girl,  as  the  case 
may  be.  Giving  up  for  a  while,  or  "toughing  it  out "  with 
the  blues,  or  losing  a  little  time  from  business,  will  not 
hurt,  but  will  restore  strength,  while  a  stimulant  will 
leave  him  less  of  a  man  than  before. 

Nervousness.  —  The  attempt  to  divide  the  race  into  brain  workers, 
muscle  workers,  and  loafers,  whether  men  or  women,  is  a  powerful  factor 
in  race  degeneration.  Leonard  Hill  says :  "  Hysteria  and  nervous 
exhaustion  are  the  fruits  not  of  overwork,  but  of  lack  of  varied  and 
interesting  employment.  The  absurd  opinion  that  hard  work  is  menial 
and  low,  leads  to  most  pernicious  consequences.  The  girl  who.  turning 
from  brain  work  to  manual  labor,  can  cook,  scrub,  wash,  and  garden, 
invites  the  bloom  of  health  to  her  cheeks;  while  the  fine  do-nothing 
lady  loses  her  good  looks,  suffers  from  the  blues,  and  is  a  nuisance  to 
her  friends  and  a  misery  to  herself.'1  A  Japanese  lady  holds  views 
similar  to  those  of  Dr.  Hill.     Read  footnote.1 

1  Statement  by  Madame  Toyi  Niku  of  Yeddo,  Japan,  after  a  six  months' 
visit  to  the  United  States.  —  "Worry  and  inactivity,  it  seems  to  me,  sharply 


THE  NERVOUS  SYSTEM  141 

Subjects  for  Debate.  —  (1)  Does  the  Chinese  woman  deform  her 
body  less  than  the  Caucasian  woman  and  suffer  less  from  it  ?  (2)  Does 
as  much  disease  originate  in  the  dining  room  as  the  barroom  ? 
(3)  Are  drugs  a  necessary  evil  ?  (4)  Does  pride  cause  as  much  illness 
as  ignorance  ?  (5)  Is  it  ever  right  to  neglect  the  health  ?  (6)  Does 
the  mind  or  the  way  of  living  have  more  effect  upon  the  health  ? 

Disuse  and  Degeneration.  —  Many  persons  in  civilized  countries 
cherish  a  vain  hope  of  having  sound  muscles  without  habitual  use  of  U 
them,  pure  blood  without  deep  breathing,  a  strong  circulation  in  an 
inactive  body,  a  fresh  skin  without  keeping  the  body  sound,  a  hearty 
appetite  without  enough  physical  labor  to  use  the  food  already  eaten, 
steady  nerves  with  a  part  of  the  body  overworked  and  a  part  stagnating 
from  disuse.  Their  flabby  muscles,  pale  skins,  highly  seasoned  food  to 
arouse  appetite,  narcotics  to  deaden  irritable  nerves,  and  the  wide  use  of 
drugs  as  a  fancied  substitute  for  right  living  all  show  the  attempt  to  be 
a  miserable  failure.  If  the  parents  leading  such  a  life  escape  with  fairly- 
good  health  and  average  length  of  life,  they  leave  a  few  unhealthy  chil- 
dren in  whom  physical  degeneration  is  plain.  Complete,  balanced  liv- 
ing only  prevents  degeneration.  Although  there  are  cases  of  illness 
which  are  not  necessarily  a  disgrace,  disease  usually  originates  in  weak- 
ness of  character  or  lack  of  common  sense.  The  snob  who  thinks  him- 
self above  physical  labor,  the  dupes  who  at  the  bidding  of  avaricious 
fashion  mongers  think  more  of  clothes  than  of  a  free  body,  the  narrow, 
unbalanced  man,  who  concentrates  all  his  energies  on  one  ambition,  the 
short-siehted  one  who  worries,  all  grow  into  a  diseased  state. 


mark  the  women  of  your  middle  classes.  I  did  not  attempt  to  study  your 
leaders  of  society,  for  they  are  much  alike  the  world  over — the  same  fuss, 
the  same  display  of  jewels  and  finery,  the  same  scandals,  the  same  uselessness. 
Your  women  do  not  diversify  enough.  If  they  are  good  cooks,  they  stop 
there  ;  perhaps  another  is  a  good  housekeeper,  another  can  sew  finely;  but 
doing  one  thing  makes  narrow-mindedness.  In  Japan  we  strive  to  do  many 
things.  The  worry  troubles  of  your  women,  it  seems  to  me,  come  largely  from 
improper  eating  and  overeating.  I  have  sat  at  many  of  your  tables  and  there 
is  too  much  food  on  them  and  too  much  variety.  First,  women  overeat,  then 
they  doctor,  then  they  starve,  and  then  they  become  nervous.  A  woman's  diet, 
especially  a  mother's,  should  always  be  simple.  Cut  down  eating  and  increase 
variety  of  labor  and  exercise.  My  own  people  live  that  way  with  a  result  that 
we  have  better  feminine  bodies,  better  skins,  and  better  tempers  than  your 
women.  I  like  the  brightness  of  your  young  women.  Perhaps  you  will  take 
the  hideous  hats  off  them  some  day,  find  a  substitute  for  the  bad  corset,  and 
let  them  wear  clothes  that  are  loose,  yet  are  soft  and  clinging.  They  are  bound 
up  in  their  clothes  too  much  now  and  their  judgment  of  colors  and  combina- 
tions is  not  good.  Their  clothing  is  either  garish  or  very  dull  in  hue.  The 
simplest  girl  in  Japan  knows  how  to  harmonize  color  with  herself.  —  Mother's 
Magazine,  November,  1907, 


CHAPTER    IX 


THE    SENSES 


Experiment  r.  Where  are  the  Nerves  of  Touch  most  Abundant  ?  — 
Open  a  pair  of  scissors  so  that  the  points  are  one  eighth  of  an  inch 
apart,  and  touch  both  points  to  the  tip  of  the  finger.  Are  they  felt  as 
one  or  as  two  points  ?  Find  how  far  they  must  be  separated  to  be  felt 
as  two  points  when  applied  to  the  back  of  the  neck.  Record  results. 
Caution:  The  person  should  be  blindfolded,  or  should  look  away  while 
the  tests  are  being  made.  Two  pins  stuck  in  a  cork  will  be  more  con- 
venient to  use  than  scissors. 

Experiment  2.  Nerves  of  Temperature,  or  Thermic  Nerves.  —  Draw 
the  end  of  a  cold  wire  along  the  skin.     Does  the  wire  feel  cold  all  the 

time  ?  Repeat  with  a  hot  wire.  Do 
you  conclude  that  temperature  is  felt 
only  in  spots  ? 

Muscular  Sense.  —  Experiment  3. 
Make  tests  of  the  ability  to  distin- 
guish the  weight  of  objects  weighing 
nearly  the  same,  when  laid  by  another 
in  outstretched  hand  ;  also  by  laying 
them  in  the  hand  while  it  rests  upon 
a  table.     Which  test  showed  more 
delicate  distinctions  ?    In  which  were 
muscles  brought  into  use  ?     Experi- 
ment 4.    Close  the  eyes  and  let  some 
one  move  your  left  arm  to  a  new  position  ;  then  see  if  you  can  with  the 
forefinger  of  the  right  hand  touch  the  forefinger  of  the  left  hand  in  its 
new  position  at  the  first  attempt. 

Experiment  5.  Functions  of  the  Several  Parts  of  the  Tongue. — 
Test  the  tip,  edges,  and  back  of  the  tongue  with  sugar,  vinegar,  qui- 
nine, and  salt.  Where  is  the  taste  of  each  most  acute  ?  Record  results. 
Flavors.  —Experiment  6.  Blindfold  a  member  of  the  class,  and 
while  he  holds  his  nostrils  firmly  closed  by  pinching  them,  have  him 
place  successively  upon  his  tongue  a  bit  of  potato  and  of  onion.  Can  he 
distinguish  them  ?     Experiment  7.     Mark  Rafter  each  of  the  following 

142 


Fig.  119. —  "Cold"  Spots  (light 
shading).  "  HOT"  SPOTS  (dark), 
skin  of  thigh. 


THE   SEXSES  1 43 

foods  that  have  a  flavor  (see  text)  :  vanilla,  apple,  lemon,  beef, 
peaches,      grapes,      coffee,      onion.      potato,      cinnamon. 

Experiment  8.  A  Smelling  Contest.  —  Place  the  following  and  other 
things  having  taste  in  vials  around  which  paper  has  been  pasted  to  con- 
ceal their  contents  :  pepper  sauce,  vinegar,  kerosene,  flavoring  extracts 
(diluted),  several  perfumes,  iodine,  bits  of  banana,  lemon,  apple,  etc. 
Number  the  vials  and  have  pupils  test  and  write  results  in  a  list. 
Correct  the  lists  and  announce  pupil  having  keenest  sense  of  smell. 

Experiment  9.  A  tasting  contest  may  be  arranged  in  a  similar 
way.  Smelling  and  tasting  tests  should  be  made  quickly  as  these 
senses  are  soon  dulled  by  repeating  a  sensation. 

Experiment  10.  Advantage  of  Two  Eyes  over  One.  —  Try  to  touch 
forefinger  to  something  held  by  another  at  arm*s  length  from  you, 
bringing  the  finger  in  from  the  side:  (1)  with  one  eye  closed; 
(2)  with  both  eyes  open.  Result  ?  Conclusion  ?  We  tell  the  dis- 
tance of  an  object  by  the  amount  of  convergence  of  the  eyeballs  needed 
to  look  at  it. 

Experiment  II.  Duration  of  Impression. — Whirl  a  stick  with  a 
glowing  coal  on  one  end  (see  Fig.   123). 

Experiment  12.  Color  Blindness.  —  Provide  a  number  of  yarns  of 
different  tints,  and  the  same  tints.  Test  color  blindness  by  having  each 
pupil  match  tints  and  assort  the  yarns. 

Experiment  13.  Fatigue  of  Optic  Nerve.  —  Gaze  long  and  steadily  at 
a  moderately  bright  object,  then  close  the  eyes.    Result  ?    Conclusion  ? 

Experiment  14.  Dissection  of  Eye.  —  The  eye  of  an  ox  is  an  in- 
teresting subject  for  dissection.  The  lens  is  like  a  clear  crystal.  Make 
out  all  parts  named  in  the  text  (see  Fig.  122). 

Experiment  15.  Image  formed  by  a  Convex  Lens.  —  For  a  few 
cents  obtain  from  a  jeweler  a  convex  lens,  or  use  a  strong  pair  of 
spectacles  worn  by  an  old  person.  Hold  the  lens  a  few  feet  from  a 
window  (darken  any  other  windows  near).  A  little  beyond  the  lens 
hold  a  white  card  or  book  open  at  a  blank  page  to  catch  the  image. 
Have  some  one  walk  before  the  window. 

Experiment  16.  Work  of  Iris.  —  Notice  the  size  of  the  pupils. 
Cover  one  eye  with  the  hand  for  a  few  minutes.  Uncover  and  look  in 
a  mirror.  Gaze  at  bright  window  and  look  again  in  the  mirror.  Con- 
clusion ?  Do  the  two  pupils  still  keep  the  same  size  when  one  eye  is 
shaded  ? 

Experiment  17.  Accommodation.  —  By  holding  your  finger  or  a 
pencil  in  line  with  writing  on  the  blackboard,  you  find  that  you  cannot 
see  both  finger  and  blackboard  distinctly  at  the  same  time  —  first  one 
and  then  the  other  is  distinct.     Explain  (see  text). 


144  J/ I'M  AX  BIOLOGY 

Experiment  18.  Astigmatism  (effect  of  unequal  curvature  of  cornea 
or  lens  along  certain  lines).  With  end  of  crayon  draw  about  twelve 
straight,  even  lines  crossing  at  one  point  on  the  blackboard.  Have 
the  lines  of  equal  distinctness.  How  many  pupils  report  that  the  lines 
in  certain  directions  are  blurred?  Inquire  whether  these  pupils  have 
frequent  headaches  from  eye  strain. 

Experiment  19.  Can  Sound  reach  the  Ear  through  the  Bones?  — 
Hold  a  watch  between  the  lips  and  notice  its  ticking.  Close  the  teeth 
down  upon  it  and  notice  any  change  in  the  sound.  Cover  one,  then 
both  ears,  and  note  the  result. 

Experiment  20.  Test  keenness  of  hearing  by  having  pupils  walk 
away  from  a  ticking  watch  until  it  becomes  inaudible.  Test  each 
ear.     A  "  stop  "  watch  is  preferable. 

Experiment  21 .  Advantage  of  Two  Ears  over  One.  —  Have  the  class 
stand  in  a  circle.  Blindfold  some  one  and  place  him  in  the  middle  of 
the  circle.  Let  various  pupils  clap  the  hands  as  the  teacher  points  to 
each.  Can  the  blindfolded  one  point  in  the  direction  whence  the  sound 
comes  ?  Stop  one  ear  with  a  handkerchief  and  repeat.  Result?  Con- 
clusion? From  what  two  points  in  the  circle  does  the  sound  fall  upon 
both  ears  alike  ? 

Experiment  22.  The  Cause  of  Nasal  Tones.  —  Let  a  pupil  go  to  the 
back  of  the  room  and  read  a  paragraph,  and  hold  his  nose  until  partly 
through  the  reading.  Or  the  teacher  may  read  with  his  face  and  hand 
hidden  by  a  large  book.  Let  the  other  pupils  raise  their  hands  when 
they  notice  a  change  in  the  quality  of  the  readers  voice.  Does  the 
experiment  show  that  a  k>  nasal  "  tone  comes  partly  through  the  nose 
or  through  the  mouth  only  ?  Does  stoppage  of  the  nostrils  by  catarrh 
cause  a  nasal  tone? 

Five  Differences  between  Special  and  General  Sensation.  —  First,  the 
nerves  of  special  sense  all  end  in  special  organs  at  the  surface ;  for 
instance,  the  touch  corpuscles  are  for  touch,  the  eye  is  for  sight,  etc. 
There  are  many  nerves  in  the  body  that  do  not  end  in  special  organs ; 
these  nerves  give  what  is  called  general  sensation.  A  second  difference 
is  that  general  sensation  tells  of  the  condition  of  the  interior  of  the  body, 
while  special  sensations  tell  us  of  the  condition  of  the  surface  of  the 
body  and  of  the  outside  world.  Third,  general  sensations  are  not  so 
exact  as  the  reports  of  the  special  senses.  One  can  locate  a  point  on 
the  skin  that  has  been  touched  much  more  accurately  than  he  can  locate 
an  internal  pain.  A  fourth  difference  is  that  the  meaning  of  each  special 
sensation  must  be  learned  (usually  in  infancy)  ;  but  the  meaning  of  gen- 
eral sensations  is  inherited.  This  inherited  knowledge  of  what  general 
sensations  mean  is  also  called  instinct.     Fifth,  the  sympathetic  nerves 


THE   SENSES  145 

usually  bring general  sensations ;  the  spinal  and  cranial  nerves  usually 
bring  special  sensations. 

Examples  of  general  sensations  are  hunger,  thirst,  satiety,  nausea, 
faintness,  giddiness,  fatigue,  weight,  aching,  shuddering,  restlessness, 
blues,  creepy  feeling,  tingling,  sleepiness,  pain,  illness.  Any  nerve  can 
convey  the  general  sensation  of  pain,  if  injured  along  its  course.  If  a 
nerve  of  touch  is  cut,  there  is  no  sensation  of  touch,  but  of  pain.  Touch 
sensations  come  only  from  the  ends  of  the  nerves.  General  sensations 
are  of  many  kinds.  We  are  only  half  conscious  of  some  of  them  ;  many 
of  them  are  hard  even  to  describe. 

Hygiene  of  the  General  Sensations.  —  General  sensation  is  an  invalu- 
able aid  to  the  health.  Without  it  as  a  guide,  the  body  could  not 
remain  alive  a  single  day.  Pain  should  be  heeded  as  our  best  friend, 
and  not  killed  with  poisonous  drugs  as  if  it  were  our  worst  enemy. 
We  should  not  deaden  the  stomach  ache  with  an  after-dinner  cigar. 
If  we  do  not  go  to  bed  when  sleepy,  the  desire  for  sleep  may  leave  us, 
and  we  will  undergo  untold  suffering  from  sleeplessness.  Thirst  should 
be  satisfied  with  cool  water,  which  quenches  it  the  best ;  he  who  makes 
his  teeth  ache  with  ice  water  will  inflame  his  stomach  and  be  continually 
thirsty.  He  who  does  not  stop  eating  when  his  hunger  is  satisfied,  will 
distend  his  stomach  with  food,  and  the  stretched  organ  will  be  harder 
to  satisfy  thereafter;  in  fact,  eating  after  a  feeling  of  satiety  may  cause 
indigestion  so  that  the  cells  will  not  get  the  food.  A  dyspeptic  is  always 
hungry,  for  the  cells  are  starving.  Fatigue  of  body  or  mind  gives  us 
wise  counsel ;  but  this  feeling  may  be  deadened  by  alcohol  or  tobacco, 
and  work  continued  until  the  body  is  injured.  We  should  heed  the 
warning  of  pain  or  fatigue  or  restlessness  as  promptly  as  an  engineer 
heeds  a  red  flag  on  the  railway  track.  One  who  uses  narcotics  acts 
like  a  reckless  engineer  who  removes  the  danger  signal  and  goes  ahead, 
hoping  by  good  luck  to  escape  an  accident. 

Most  of  the  nerves  of  touch  end  in  papillae  of  the  dermis 
as  microscopic,  egg-shaped  bodies  (Fig.  120).  There  are 
also  many  in  the  interior  of  the  mouth,  especially  on  the 
tongue.  On  the  palms  they  are  arranged  in  curved  lines, 
and  on  the  tips  of  the  fingers  they  are  in  circular  lines, 
with  one  papilla  in  the  center.  The  delicacy  of  the  sense 
of  touch  varies  very  much  in  different  parts  of  the  skin. 
This  delicacy  refers  to  two  things :  the  ability  to  feel  the 
slightest  pressure  and  the  ability  to  tell  the  exact  point  of 


146 


HUMAN  BIOLOGY 


Fig.  120.  —  Different  Kinds  of  Touch 
Bodies  at  Ends  of  Nerves. 

A,  from  cornea  of  the  eye  ;  B,  from  the  tongue  of  a 
duck  ;   C,  D,  E,  from  the  skin  of  the  fingers.      (Jegi.) 


the  skin  that  is  touched.     A  lighter  pressure  can  be  felt 
on  the  forehead   and  temples  than   with   any  part  of  the 

body.  (Why  is  it  best 
for  this  to  be  the 
case  ?)  The  greatest 
delicacy  in  locating 
the  point  of  the  skin 
touched  is  found  to  be 
tocated  in  the  tip  of 
the  tongue,  the  lips, 
and  the  ends  of  the 
fingers  (Exp.  1). 
(Why  is  it  best  that 
this  is  so  ?)  This  deli- 
cacy is  least  in  the 
middle  of  the  back. 
The  delicacy  varies 
with  the  number  of  touch  corpuscles  in  different  parts 
of  the  skin.  The  sense  of  touch  is  capable  of  great 
cultivation,  as  in  the  case  of  the  blind. 

The  temperature  sense  is  given  by  special  nerves  called  the  thermic 
nerves  (Exp.  2).  That  the  thermic  nerves  are  easily  fatigued  is  noticed 
soon  after  entering  a  bath  of  hot  water;  it  is  also  shown  by  the  fact 
that  in  cold  countries  the  nose  or  ears  of  a  person  may  freeze  without 
his  feeling  it. 

The  Muscular  Sense.  —  The  special  sense  of  touch  gives  some  sense  of 
weight.  A  weight  upon  the  skin  must  be  increased  by  one  third  before 
it  feels  heavier,  but  by  lifting  an  object  so  as  to  bring  into  action  the 
muscular  sense  residing  in  nerves  ending  in  the  muscles  an  increase  of 
only  one  seventeenth  of  the  original  weight  can  be  noticed  (Exp.  3). 
This  sense  gives  us  a  continual  account  of  the  position  of  the  limbs 
(Exp.  4). 

The  end  organs  of  taste  are  located  in  the  papillae  of 
the  tongue.  The  tongue  has  a  fuzzy  look  because  of  the 
numerous  papillae. 


THE   SENSES  1 47 

The  principal  tastes  are  only  four  ;  namely,  sweet  (tasted 
chiefly  by  tip  of  tongue),  sour  and  saline  (sides  of  tongue), 
bitter  (tasted  on  the  back  of  tongue)  (Exp.  5). 

The  nerves  of  smell  end  in  the  mucous  membrane  of  the 
upper  half  of  the  two  nasal  chambers  ;  the  fibers  are  spread 
over  the  upper  proportion  of  the  walls.  The  direct  current 
of  air  does  not  pass  as  high  as  these  nerve  endings  ;  hence 
sniffing  aids  the  perception  of  odors.  This  sense  is  able 
to  bring  up  the  associations  of  early  life  more  powerfully 
than  any  of  the  senses.  The  odor  of  a  flower  like  one 
that  grew  in  an  old  garden  can  almost  restore  the  con- 
sciousness of  the  past.  We  smell  gases  only  ;  solids  and 
liquids  cannot  affect  this  pair  of  nerves  (Exp.  8). 

Flavors.  —  The  tastes  that  we  call  flavors  are  really 
smells.  We  confuse  them  with  taste,  because  they  accom- 
pany food  that  is  in  the  mouth.  Name  some  foods  that 
seem  "  tasteless  "  when  one  has  a  severe  cold  in  the  head. 
Why  is  this  ?  Some  of  the  most  repulsive  drugs  can  be 
easily  swallowed  if  the  nose  is  held  (Exp.  6  and  7). 

Hygiene  of  the  Senses  of  Taste  and  Smell.  —  A  savage, or  a  beast 
uses  the  senses  of  taste  and  smell  to  find  out  whether  things  are  good 
to  eat  or  not.  If  a  civilized  man's  senses  are  not  perverted,  and  he  eats 
only  simple  foods  that  have  a  pleasant  taste,  they  will  not  injure  him  or 
cause  him  sickness.  Things  that  are  poisonous  usually  have  unpleasant 
tastes  and  often  have  unpleasant  odors.  These  senses  are  naturally 
of  wonderful  delicacy.  They  can  be  cultivated  to  a  still  more  remark- 
able degree,  or  they  can  be  blunted  and  almost  destroyed.  Chronic 
catarrh  dulls  or  destroys  the  sense  of  smell.  The  loss  or  even  the 
weakening  of  the  perception  of  flavors  is  an  injury  to  the  working  of 
the  closely  related  sense  of  taste.  When  a  person  loses  the  enjoyment 
of  delicate  flavors,  he  wants  food  to  have  strong  seasoning  and  more 
decided  taste  to  prevent  it  from  being  insipid.  Everything  must  be 
either  very  greasy  or  very  sweet  or  very  salty  or  very  sour,  to  please  his 
degenerate  senses.  Wheat,  corn,  and  other  grains  have  each  its  own 
pleasant  taste,  yet  such  persons  must  have  lard  in  their  bread  because 
they  are  not  capable  of  appreciating  anything  with  a  delicate  taste.     In 


148  HUMAN  BIOLOGY 

England,  butter  is  not  salted  and  its  delicate  taste  is  enjoyed :  in 
America,  salt  is  added  to  preserve  it,  and  most  people  have  come  to 
prefer  the  strong  taste  of  salty  butter  to  the  delicate  taste  of  pure  butter, 
and  do  not  like  it  unless  its  true  taste  is  partly  hidden  by  the  taste  of 
salt  (Exp.  9). 

Deceiving  the  Sense  of  Taste.  —  The  habit  of  using  narcotics  like 
tea  and  coffee  is  usually  begun  by  concealing  the  repulsive  bitter  taste 
of  the  substance  by  mixing  sugar,  cream,  and  other  agreeable  things 
with  it.  Licorice  is  sometimes  mixed  with  tobacco  to  weaken  its  biting 
taste.  Pure  alcohol  would  never  be  drunk  by  any  one  who  had  the 
least  respect  for  the  sense  of  taste,  but  the  agreeable  flavor  of  grapes, 
apples,  and  other  fruit  which  still  remains  in  wine,  cider,  and  brandy, 
conceals  the  repulsive  taste  of  the  alcohol.  Beer  has  the  insipid  taste 
of  grain  which  has  undergone  decomposition  or  partial  rotting,  and 
hops  are  added  because  the  strong  bitter  taste  of  hops  is  needed  to 
hide  the  stale,  rancid  taste  of  the  rotted  grain.  Eggnog  is  made  of 
eggs,  a  nourishing  food;  sugar,  which  has  an  agreeable  taste;  water,  a 
refreshing  drink,  and  alcohol,  a  fiery  poison.  A  very  good  eggnog  is 
often  made  without  alcohol,  but  a  good  one  could  hardly  be  made  with 
any  of  the  pleasant  ingredients  left  out.  The  best  eggnog  is  made  by 
using  the  fresh  juice  of  lemon,  orange,  or  grape,  instead  of  alcohol. 

Effect  of  Narcotics.  —  Tobacco,  alcohol,  opium,  and  other  narcotics 
dull  the  senses  of  taste  and  smell  and  prevent  the  enjoyment  of  delicate 
flavors.  They  accomplish  this  as  much  by  their  effect  upon  the  brain 
as  upon  the  nerves  themselves. 

It  is  Wrong  to  eat  Food  that  is  not  Relished.  —  Unpalatable  food  is 
not  likely  to  be  well  digested.  It  is  a  law  of  the  body  that  the  food 
which  is  enjoyed  the  most  is  digested  the  best.  This  applies  to  a  hungry 
person  eating  food  with  its  own  honest  taste,  not  to  food  disguised  by 
the  taste  of  something  else.  The  rule  does  not  apply  to  a  taste  per- 
verted by  having  been  forced  to  become  accustomed  to  poisonous 
things.  People  who  munch  their  food  slowly  enjoy  the  pleasures  of 
taste  the  most,  and  digest  their  food  the  best.  The  nerves  of  taste 
and  smell  easily  become  fatigued.  The  first  whiff  from  a  cologne  bottle 
is  the  strongest.  Highly  flavored  foods  should  be  eaten  moderately, 
if  we  would  obtain  the  greatest  enjoyment  from  them. 

Thought  Questions.  —  1.  Interfering  with  the  Body.  What  is 
the  natural  direction  of  growth  of  the  big  toe?  2.  Think  of  six  evil 
results,  direct  or  indirect,  which  will  follow  from  displacing  it  by  tight 
shoes  (p.  48).  3.  Which  part  of  the  spinal  column,  designed  in 
infinite  wisdom  to  be  most  flexible,  do  some  people  try  to  make  the 
most  inflexible?     4.    The  mobility  of  the  false  and  floating  ribs  was 


THE   SENSES 


149 


intended  as  a  blessing.  Some  people  interpret  the  blessing  as  an 
opportunity  to  do  what  ?  5.  Name  six  articles  which  warn  us  to  avoid 
them  by  their  bitter,  burning,  or  nauseating  tastes,  yet  which  are  used 
by  man.  6.  Name  six  feelings  which  are  intended  as  warnings  for  our 
guidance,  but  which  are  commonly  disregarded. 

The  eyes  on  the  rays  of  the  starfish  are  mere  spots  of 
pigment.  Insects  have  lenses  in  their  eyes.  The  eyes  of 
vertebrates  are  all  formed  on  the  same  general  plan  as  the 
human  eye. 

The  eyeballs  are  globes  about  an  inch  in  diameter. 
They  are  placed  in  deep,  bony  sockets,  called  orbits,  in 
the  front  part  of  the  skull.  The  optic  nerve,  other  nerves, 
and  several  large  blood  vessels  pass  to  the  eye  through  a 
hole  in  the  back  of  the  orbit.  A  soft  cushion  of  fat  is  in 
the  orbit  behind  the  eyeball.  A  pressure  upon  the  eye- 
ball causes  the  eye  to  sink 
into  the  socket,  for  the  fat 
yields  to  the  pressure. 
This  is  a  protection  to  the 
eye. 

The  eyelids  protect  the 
eyes  from  dust,  and  at 
times  from  the  light.  They 
are  aided  in  this  by  the 
eyelashes. 

The  tears  are  formed  by  tear  glands  situated  above  the 
eyeball  in  the  portion  of  the  orbit  farthest  from  the  nose, 
just  beneath  the  bony  brow  where  it  feels  the  sharpest 
(Fig.  121).  They  are  about  the  size  of  almonds.  A  salt- 
ish liquid  is  continually  oozing  from  the  tear  glands  and 
passing  over  the  eyeball ;  it  is  carried  into  the  nose 
through  the  nasal  duct  (Fig.  121).  The  tears  reach  this 
duct  through  two  small  canals,  which  open  into  the  eye 
in  the  little  fleshy  elevation   at  the  inner  corners    of  the 


Fig.  121.— Tear  Glands  and 
DUCTS  of  right  eye.     (Jegi.) 


150 


HUMAN  BIOLOGY 


eye  (Fig.  121).  The  opening  of  one  of  the  canals  may 
be  seen  by  looking  into  a  mirror.  Sometimes  these  canals 
are  stopped  up,  and  what  is  called  a  "weeping  eye" 
results.  A  temporary  stoppage  may  occur  during  a  cold 
in  the  head. 

Tears  prevent  friction  between  eye  and  lid.  Winking 
applies  the  tears  to  the  ball.  Small  glands  along  the 
edges  of  the  lids  form  a  kind  of  oil  which  usually  prevents 
the  tears  from  flowing  over  the  lids.  Sometimes  this  oily 
secretion  is  so  abundant,  especially  during  sleep,  as  to 
cause  the  lids  to  stick  together.     The  mucous  membrane 

of  the  eyelids 
continues  as  a 
transparent 
membrane  (the 
conjunct  iva) 
which  passes 
over  the  front  of 
the  ball. 

The  globe  of 
the  eye  consists 
of  its  outer  wall 
and  the  soft  con- 
tents (Fig.  122). 
The  wall  has  three  layers  or  coats.  The  outer  coat  is  the 
tough  sclerotic  (Greek,  skleros,  hard),  composed  of  dense 
connective  tissue  (Exp.  14).  It  gives  strength  and  firm- 
ness to  the  eyeball.  It  shows  between  the  lids  as  the 
"white  of  the  eye."  It  is  white  and  opaque  except  in 
front;  there  it  bulges  out  to  form  the  transparent  cornea. 
This  clear  portion  of  the  wall  may  be  seen  by  looking  at 
the  eye  of  another  from  the  side. 

The  second  coat,  called  the  choroid,  consists  of   blood 


Retina 
Choroid 
'sclerotic  coat 


Fig.  122.  —  The  Anatomy  oy  the  Eve. 


THE   SENSES 


151 


vessels  and  a  loose  connective  tissue  containing  many 
dark  brown  or  black  pigment  granules.  The  choroid 
absorbs  superfluous  light.  Cats'  eyes  shine  at  night 
because  this  coat  in  their  eyes  reflects  some  light.  The 
choroid  separates  from  the  sclerotic  toward  the  front  of 
the  eye  and  forms  the  colored  iris.  The  iris  makes  the 
eyes  beautiful,  and  it  also  serves  the  useful  purpose  of 
regulating  the  amount  of  light.  The  hole  in  the  iris  is 
called  the  pupil  (Exp.  15). 

The  third  and  innermost  coat,  the  sensitive  pinkish  layer 
called  the  ret'in-a,  is  the  most  important  and  characteristic 
tissue  in  the  eye.  It  re- 
ceives the  light  rays,  and 
retains  the  image  for  a 
fraction  of  a  second  (Exp. 
1 1 ).  Hence  the  pictures 
in  a  kinetoscope  (Fig.  123) 
appear  as  one  moving  pic- 
ture. The  retina  is  made 
chiefly  of  the  fibers  of  the 
optic  nerve.  This  nerve 
contains  about  five  hundred 
thousand  fibers,  and  enters 
at  the  back  of  the  ball. 
The  spot  where  it  enters 
contains  no  nerve  endings 
and  is  not  sensitive  to 
light.  It  is  called  the 
blind  spot.  The  spot  where  the  light  most  often  falls  is 
most  sensitive  to  light.      It  is  the  yellow  spot  (Fig.  122). 

Test  for  the  Blind  Spot.  —  In  this  experiment  shut 
the  right  eye  and  be  careful  not  to  let  the  left  eye 
waver. 


Fig.  123.  —  Stroboscope,  the  original  of 
the  kinetoscope.  The  observer  looks 
through  the  slits  of  a  rapidly  revolving 
disk  and  a  new  image  falls  on  the  retina 
before  the  last  image  has  faded.  Com- 
pare the  pictures  in  the  figure. 


152  HUMAN  BIOLOGY 

*  Read  this  line  slowly.  Can  you  see  the  star  all  the 
time  ?  (If  so,  hold  the  book  farther  or  closer  and  repeat.) 
Within  the  coats  of  the  ball,  like  the  pulp  within  the 
rind  of  an  orange,  are  the  soft  contents,  divided  into  three 
parts.  The  first  is  a  watery  liquid  in  front,  which  serves 
to  keep  the  cornea  bulged  out  (Fig.  122).  It  is  called  the 
aJque-ous  humor.  The  main  cavity  of  the  ball  is  occupied 
by  a  clear,  jellylike  substance  called  the  vifre-ous  humor, 
which  serves  to  keep  the  ball  distended.  Back  of  the  iris, 
and  separating  the  two  humors  just  named,  is  the  crystal- 
line lens,  a  beautiful  clear  lens,  convex  or  rounded  out  on 
both  sides  (Exp.  14).  It  serves  to  bring  the  light  to  a 
focus  on  the  retina,  thereby  forming  images  of  outside 
objects. 

The  eye,  like  a  camera,  has  a  dark  lining,  the  choroid ; 
the  retina  corresponds  to  the  sensitive  plate,  and  the  lens 
brings  the  rays  to  a  focus  on  it  and  forms  the  image. 

The  Path  of  Light  in  the  Eye.  — The  light  enters  through 
the  transparent  cornea  and   passes  through  the  aqueous 

humor.  As  it  goes  through 
the  pupil,  the  iris  shuts  off  all 
the  light  that  is  not  needed. 
The  crystalline  lens  receives 
the  light  that  has  been  al- 
lowed to  pass,  and  so  bends 
the  rays  that  by  the  time  they 

Fig.    124.  — Crossing    of    Optic       have  passed  through  the  vit- 
Nerves  showing  that  one  nerve  .      _  ,■%  r    n     ,,^^„ 

.„,.,,  reous   humor  they  fall   upon 

reaches  same  half  of  both  eyes.  J  l 

the  retina  in  just  the  right 
way  to  form  a  tiny  image  of  anything  outside  (Exp.  11). 
The  choroid  absorbs  any  light  that  passes  the  retina. 
The  iris  and  choroid  of  albinos  have  no  pigment;  hence 
albinos  squint  their  eyes  to  shut  out  some  of  the  light. 


THE   SENSES 


153 


FlG.  125.  —  Change  of  lens  in  accom- 
modation.    (Jegi.) 


Accommodation.  —  In  order  to  focus  the  light  upon  the 
retina,  the  lens  must  change  shape  for  every  change  in  the 
distance  of  the  object  looked 
at  (see  Fig.  125).  The  shape 
of  the  lens  can  be  readily 
changed,  for  it  is  elastic  and 
has  muscular  fibers  around 
its  edges  (Exp.  17). 

Defects  in  the  Eye.  —  Some 
eyeballs  are  too  long,  and  the  lens  brings  the  rays  to  a 
focus  before  they  reach  the  retina.     Such  eyes  are  near- 

sigJited  (Fig.  126)  and  require 
glasses  that  round  inward  (con- 
cave). Some  eyeballs  are  too 
flat,  and  the  rays  are  not  brought 
to  a  focus  soon  enough.  Such 
eyes  are  farsigJited  and  require 
glasses  that  round  outward 
(convex).  See  Fig.  127.  (Re- 
peat Exp.  15.) 

Care  of  the  Eyes.  —  Because 
the  eyes  can  do  a  large  amount 
of   work   without    giving    pain, 
they  are  often  abused.     When 
reading  or  doing   intricate  work,  turn  the  eyes  from  the 

work  occasionally  and  look 
at  some  distant  object ;  stop 
work  before  the  eyes  are 
tired.  Twilight  of  early 
evening  has  ruined  many 
good     eyes.      You     should 

FIG.     I27.-FARSIGHTED     EYE     (ball  r]  ^^        ^^ 

too  short)  which  needs  convex  lens  J  l 

to  focus  rays  upon  retina.  the  twilight  begins,  for  the 


Fig.  126.  —  (1)  Nearsighted 
Eye  (ball  too  long),  which  only 
focuses  rays  for  near  objects 
(2)  when  concave  glasses  are 
used  (3). 


154  HUMAN  BIOLOGY 

light  fades  so  gradually  that  you  will  surely  be  straining 
the  eyes  before  you  know  it.  Do  not  work  with  the  light 
in  front ;  the  glare  of  the  light  makes  objects  appear  dim. 
The  light  should  come  from  above,  and  (for  right-handed 
people)  from  the  left.  Do  not  read  papers  or  books 
printed  in  fine  type.  We  should  not  read  when  convales- 
cing from  illness  ;  with  the  head  bent  down ;  when  the 
eyes  are  sore ;  in  jolting  cars.  Heating  the  eyes  by  a 
burner,  or  drying  the  eyeballs  in  a  dry,  stove-heated  at- 
mosphere, using  a  light  without  a  shade,  cause  trouble 
with  students'  eyes.  Of  what  are  blood-shot  eyes  often  a 
sign?  Our  eyes  are  best  suited  for  seeing  at  a  distance 
because  primitive  man  had  no  houses,  books,  sewed 
clothes.  Effort  is  required  to  shape  the  lens  for  seeing 
near  objects.  Most  cases  of  nearsightedness  begin  when 
children  are  taught  to  read  under  eight  years  old.  The 
eyes  are  sometimes  injured  by  the  use  of  tobacco. 

Thought   Questions.     The  Eye.  —  1.    The   eye  is  shielded  from 

blows  by  bony  projections  of  — — ,  ,  and  .     2.    The  hairs  of 

the  eyebrows  lie  inclined  toward  ,  in  order  to  turn  from  the 

.     3.    I  rind  by  trying  it  that  I   (can  or  cannot?)  see  the  position 

of  a  window  with  my  eyes  closed.     4.    The  pupil  appears  to  be  black, 

because  no is from  the  interior  wall  of  the  eye.     I  know  that 

the  iris  is  partly  muscle,  because  it the  size  of  the  . 

Sound.  —  Anything  that  is  sending  off  sound  does  so  by  vibrating, 
or  shaking  to  and  fro,  very  rapidly.  For  instance,  a  vibrating  viohn 
string  sets  every  particle  of  air  near  it  swinging  to  and  fro.  The  near- 
est particles  of  air  strike  the  next  ones  and  bounce  back,  these  in  turn 
strike  against  others,  and  thus  vibrations  called  sound  waves  are  sent 
through  space  in  all  directions  from  the  sounding  body.  We  feel  these 
waves  with  the  ear. 

The  ear  consists  of  three  portions  :  the  external  ear,  the 
middle  ear  (or  drum),  and  the  iutej-nal  ear  (or  labyrinth, 
see  Fig.  128).  The  cranial  nerve  connecting  the  ear  with 
the  brain  is  called  the  auditory  nerve.     The    outer   and 


THE   SEXSES 


155 


middle  ear  pass  on  the  vibrations  of  air  to  the  ends  of  the 
fibers  of  the  auditory  nerve  in  the  internal  ear. 

The  external  ear  consists  of  a  large  wrinkled  cartilage 
on  the  exterior  of  the  head  and  a  canal  leading  from  it, 
called  the  meatus.  This  passage  is  closed  at  its  inner  end 
by  the  drum  membrane  ox  drum  skin.  It  is  often  called 
the  drum,  but  this  name  is  properly  applied  to  the  whole 
middle  ear.     A  trial  will  show  that  the  drum  skin  cannot 


Meatu 

The  Drum  ■ 

of  the  Ear  ~ — -i 

{Tympanic 

Membrane 


The 
Shell  Tube 
{Cochlea). 


The  Anvi] 
(*«*  *»m«.*  Eustachian  Tube 

Fig.  128.  —  Middle  and  Internal  Ear  (greatly  enlarged). 


be  seen  even  with  the  aid  of  a  bright  light,  for  the  passage 
is  slightly  curved  (see  Fig.  128).  Hence  a  missile  or  a 
flying  insect  cannot  go  straight  against  the  ear  drum.  The 
skin  lining  this  passage  contains  wax  glands,  which  secrete 
a  bitter  sticky  wax,  which  helps  to  keep  the  passage  flex- 
ible. This  wax  catches  dust  and  usually  stops  insects  that 
may  enter.  If  an  insect  enters  the  ear,  it  may  often  be 
coaxed  out  by  a  bright  light  held  close  to  the  ear.  The 
ear  wax  in  a  healthy  ear  dries  with  dust  and  scales  of  epi- 
dermis and  falls  out  in  flakes,  thus  cleansing  the  ear.     It 


I56  HUMAN  BIOLOGY 

is  unwise  to  probe  into  the  ear  with  a  hard  object  or  even 
with  the  corner  of  a  towel.  It  is  not  necessary  to  insert 
the  finger  in  the  meatus  to  cleanse  it ;  it  is  one  inch  long, 
but  only  about  one  fourth  inch  across.  (How  large  is  the 
little  finger  ?)  The  cartilaginous  ears  on  the  sides  of  the 
head  should  be  carefully  washed  because  of  their  many 
crevices.  If  ear  wax  is  deposited  too  fast,  it  will  cause 
temporary  deafness  and  earache.  It  may  be  syringed  out 
with  warm  water.  Earache  is  usually  caused  by  a  small 
boil  which  requires  time  to  relieve  itself  by  bursting. 
Warm  water  poured  into  the  upturned  ear,  or  hot  flannels 
or  compresses  applied  to  the  side  of  the  head  will  lessen 
the  suffering.  Each  ear  has  three  muscles  for  moving  it. 
Once  they  were  doubtless  useful  to  all,  but  like  the  scalp 
muscle  they  have  become  so  weakened  by  disuse  as  to  be 
useless  to  most  people.     They  are  vestigial  organs. 

The  middle  ear,  or  drum  chamber,  contains  air  (Fig. 
128).  It  is  separated  from  the  outer  ear  by  the  drum 
membrane.  It  contains  three  bones  which  stretch  across 
it  and  conduct  the  sound  waves  from  the  drum  membrane 
to  the  inner  ear.  State  the  order  in  which  they  are 
placed  (see  Fig.  128).  The  middle  ear  is  connected  with 
the  pharynx  by  a  tube  (the  Eustachian  tube ;  pronounced 
yoo-stake'e-an,  see  Fig.  128).  This  tube  is  opened  every 
time  we  swallow.  It  allows  the  air  from  the  throat  to 
enter  the  middle  ear  and  keep  the  air  pressure  equal  on 
each  side  of  the  drum  skin.  This  tube  and  the  middle 
ear  are  lined  with  mucous  membrane. 

A  cold  in  the  head  or  a  sore  throat  may  extend  through 
this  tube  to  the  middle  ear  and  affect  the  hearing.  This 
occurs  because  the  tube  is  closed  by  congestion  of  its  lin- 
ing ;  the  air  of  the  middle  ear  may  be  partly  absorbed, 
and  the  pressure  of  the  outside  air  may  cause  the  drum 


THE   SENSES  I  57 

membrane  to  bulge  inward,  and  to  be  stretched  so  tight 
that  it  cannot  vibrate  freely. 

The  inner  ear  is  called  the  labyrinth,  because  of  its  wind- 
ing passages.  There  is  a  spiral  passage  called  the  snail 
shell and  three  simpler  passages  called  the  loops  (Fig.  128). 
The  inner  ear  is  filled  with  a  limpid  liquid  which  conveys 
the  vibrations  to  the  ends  of  the  auditory  nerve  found  in  the 
snail  shell.  If  the  auditory  nerve  or  labyrinth  becomes 
diseased,  the  deafness  is  probably  incurable.  Quinine  and 
other  drugs  may  cause  deafness. 

Sense  of  Equilibrium.  —  Some  fibers  of  the  auditory  nerve  end  in  the 
loops  and  are  not  believed  to  be  used  in  hearing.  It  is  believed  that 
each  loop  acts  like  a  carpenter's  level,  and  the  varying  pressure  of  the 
fluid  upon  the  nerves  in  the  loops  tells  us  the  position  of  the  body  and 
constitutes  the  sense  of  equilibrium.  There  are  how  many  of  these 
loops  in  each  ear  ?     (Fig.  128.) 


CHAPTER    X 


BACTERIA   AND   SANITATION 


Experiment  i.  Yeast  Plants.  —  With  a  microscope  examine  a  drop 
from  a  glass  of  water  in  which  you  have  washed  grapes  or  apples 
(Fig.  129). 

Experiment  2.  Fermentation.  —  Put  a  tablespoonful  of  sugar  into 
this  water  and  set  the  glass  in  a  warm  place  for  a  day  or  two.     Do 

you  see  any  bubbles  of  gas  ? 
Have  the  odor  and  taste 
changed  ?  Does  the  micro- 
scope show  that  the  yeast 
plants  are  now  more  abun- 
dant ?  By  fermentation,  or 
the  growth  of  yeast  in  sugar, 
sugar  is  changed  into  carbon 
dioxid,  a  gas,  and  alcohol,  a 
liquid. 

Experiment  3.  A  Sani- 
tary Map.  —  Construct  a 
sanitary  map  of  the  com- 
munity. Indicate  houses 
where  consumption,  typhoid 
fever,  or  other  transmissible 
diseases  have  occurred,  with 
number  of  cases.  Mark  loca- 
tion of  stagnant  waters  where 
mosquitoes  breed,  mark 
garbage  dumps,  unclean  streets.  Suggest  where  improvements  may 
be  made  in  drainage,  dust,  noises,  sunshine,  shade,  etc. 

Bacteria,  or  microbes,  the  smallest  living  things,  are 
visible  only  under  a  microscope  of  high  power.  (See 
"Plant  Biology,"  p.  182.)  They  obtain  food  either  from 
dead  tissue  or  from  degenerate  tissue  of  living  plants  and 

158 


Fig.  129.  —  Yeast  Cells  magnified  200 
diameters,  or  40,000  areas).  Yeast  plants 
multiply  by  budding.  Notice  small  cells 
growing  on  larger  and  older  ones. 


BACTERIA    A. YD   SAX/TAT/OX  I  59 

animals.  The  green  plants  and  the  animals  now  upon  the 
earth  have  proved  their  fitness  to  survive  by  successfully 
resisting  these  one-celled  vegetable  germs,  or  bacteria. 
Microbe  diseases  attack  only  the  weaker  individuals  of  the 
human  species,  or  those  who  have  gone  to  regions  where 
there  are  microbes  which  their  bodies  have  not  yet  ac- 
quired the  power  of  resisting. 

Usefulness  of  Bacteria.  —  Their  chief  work  is  to  destroy 
dead  tissue  and  return  it  to  the  soil  and  air  for  the  use  of 
green  plants  again,  otherwise  the  earth  would  be  filled 
with  carcasses,  etc.  They  are  indispensable  in  soil  forma- 
tion. They  give  the  agreeable  flavors  to  butter  and  cheese, 
and  cause  milk  to  sour.  A  rod-shaped  bacterium  is  called 
a  bacillus  (Fig.  130);  a  spherical  one  is  a  coccus. 

Multiplication  of  Bacteria.  —  This  is  by  division  or  fis- 
sion. Sometimes,  instead  of  dividing,  a  little  rounded  mass 
known  as  a  spore  appears.  The  spore  breaks  out  and  the 
bacterium  itself  perishes.  Species  which  do  not  produce 
spores  are  readily  destroyed,  but  spores  have  a  hard,  tough 
shell,  and  they  may  be  dried  or  heated  even  to  boiling  with- 
out being  killed.  Spores  float  through  the  air  and  start 
new  colonies.  Most  common  bacteria  grow  best  between  Jo° 
and  950  F.  They  render  it  difficult  to  preserve  foods,  espe- 
cially proteid  foods  (cheese,  lean  meat,  eggs,  etc.).  Food 
decays  slowly  if  at  all  below  yo°  and  above  1250.  Direct 
sunlight,  or  the  temperature  of  boiling  water  (21 2°  F.) 
kills  bacteria  but  not  spores.  Pantries,  kitchen,  and  sick- 
rooms should  have  bright  walls  and  all  the  light  possible. 
Boiling  water  should  be  poured  into  the  sink,  and  dish 
cloths  should  be  thoroughly  washed  in  boiling  water. 

Diseases  due  to  Bacteria.  —  A  germ  disease  is  usually  due 
partly  or  wholly  to  substances  called  toxins  produced  by 
the  bacteria.     Most  disease  germs  attack  a  single  organ 


l6o  HUMAN  BIOLOGY 

of  the  body.     Diphtheria  is  caused  by  a  species  (Fig.   130) 

that  grows  on  the  mucous  membrane  of  the  throat ;  this 

»  germ   produces  a  powerful    toxin.     The 

^/^v*r»  V         germs    of   typhoid  fever  (Fig.    131)  and 

^4l    (Pw      Asiatic    cholera    multiply    in    the    small 

■    V"^  <f*  intestine.       In    both    these   diseases   the 

[V    ^pw*        source  of  infection  is  the  diarrhoeal  dis- 

fig.  130.— bacillus    charges  from  the  alimentary  canal.     Flies 

of  Diphtheria.  .-  .,     .     £      .    c     „, 

may  carry  the  germs  on  their  feet  irom 

the  discharge  to  food.    Sometimes  typhoid  fever  cases  occur 

throughout  a  town  because  the  water  supply  has  become 

contaminated  by  sewage.    Cases  may        ,^  .». 

occur  only  in  families  that  buy  milk      *'\v«»y^*' 

from    a   certain    dairy,    because   the     i\^.  ^\-^2 

milk  cans  have  been  washed  in  con-      ^     liC        >"%  "-/  A 

taminated  water.     In  caring  for  a  ty-       %  ^"nJ^C"       X* 

phoid  patient  all  suspicious  material      »    •  ***  V\N^~  *T  *  V 

should     be    disinfected    or    burned.        ■"*.«.   »***■*         *• 

Germs   of    tuberculosis   (called    con-      FlG^H"^A™  °F 

sumption    if    the    disease    is   in    the 

lungs)  may  float  through  the  air.     Recent  investigations 

indicate,   however,   that  infection  usually  occurs   through 

the  alimentary  canal,  the   germs  being  swallowed,   then 

absorbed  and  taken  to  the  lungs  in  the  blood  or  lymph. 

To    prevent  a  patient   from   reinfecting   himself   in    new 

parts    of    the    lungs    or   elsewhere,    he    should    carefully 

cleanse  his  teeth,   mouth,   and  throat  (by  gargling  with 

formal  or  lysol)  before  eating. 

Mosquito  Fevers. — Malaria,  yellow  fever,  and  probably 

dengue   are    transmitted    each    by    a   different    genus    of 

mosquito  (Fig.  132).     A  mosquito  of  the  malarial  genus 

may  bite  a  patient  and  suck  into  its  body  blood-corpuscles 

containing  spores  of  the   malarial   parasite  (a   protozoan 


BACTERIA   AND    SANITATION 


161 


animal,  see  "Animal  Biology,"  p.  7).  Afterwards  a  spore 
(in  another  stage)  may  be  transmitted  by  this  mosquito 
when  it  bites  another  person.  The 
germ  enters  a  red  corpuscle,  grows, 
and  finally  divides  into  many  little 
spores.  At  this  moment  the  cor- 
puscle itself  breaks  up,  setting 
free  in  the  blood  the  spores  and 
toxin  formed.  This  causes  the 
chill  and  fever.  This  develop- 
ment usually  takes  forty-eight 
hours,  hence  the  fever  occurs 
every  other  day.  These  mos- 
quitoes begin  to  fly  at  dusk.  How 
are  they  recognized?     (Fig.  132.) 

They  should  be  kept  out  of  houses    Fig.  132.  —  Culex  or  Com 

,  ,  ,,        ,      ,      ,  mon  Mosquito,  above  (pos 

by  screens  or  from  the  beds  by 

netting.       Kerosene     should     be 

poured  on  breeding  places  at  the 

rate  of  one  ounce  for  fifteen  square 

feet    of    standing    water.       This 

should  be  repeated  twice  a  month. 

Cactus  macer- 


sibly  carries  dengue  fever). 
Anopheles  or  Malarial 
Mosquito,  below  (not  always 
infected).  Body  of  malarial 
mosquito  is  never  held  paral- 
lel to  the  supporting  surface 
(unless  a  leg  is  missing) ;  it 
has  five  long  appendages  to 
the  head,  the  culex  (above) 
has  only  three.     (Draw.) 


ated  in  water 

may  be  used,  and  forms  a  permanent 

film    on   the  water.      Stagnant   pools 

may  be  filled  or  drained  (Exp.  4). 
Fig.   133.  —  Protective 

White     Corpuscle     Malarial  patients  should  themselves  be 

(phagocyte)  digesting    screened,  as  the  eJiicf  source  of  danger  to 

a  microbe.  ... 

others ;  for  only  mosquitoes  who  suck 
the  blood  of  malarial  patients  will  transmit  the  disease. 
Even  then  it  is  only  transmitted  to  those  whose  white 
blood  corpuscles  are  unable  to  protect  them  (Fig.  133). 


162 


HUMAN  BIOLOGY 


Further  Means  of  Protection  against  Disease  Germs. — 
The  best  protection  is  physical  vigor.  There  are  certain 
substances  called  opsonins  which  exist  in  the  plasma  of  the 
blood  of  disease-resisting  persons  ;  these  opsonins  give  the 
white  corpuscles  the  power  to  devour  disease  germs.  The 
scrum  of  the  blood  also  develops  antitoxins  which  neutral- 
ize the  toxins  formed  in  disease.  Not  only  can  the  white 
corpuscles  and  serum  kill  bacteria,  but  most  of  the  secre- 
tions of  the  healthy  body  (gastric  juice,  nasal  secretions, 
etc.)  are  bacteria-killing  as  well.  Persons  in  a  low  state 
of  health  most  readily  succumb  to  disease.  Excess  in  eat- 
ing may  lessen  the  germicidal  power  of  gastric  juice  and 
inactivity  that  of  the  lymph.  The  same  germ  disease 
does  not  usually  attack  the  same  person  twice,  as  the 
body  becomes  immune;  that  is,  an  opsonin,  or  an  anti- 
toxin, is  developed  which  cures  the  first  attack  and  remains 
to  protect  the  body  in  future. 

The  periods  of  quarantine  or  isolation  for  several  com- 
mon germ  diseases  are  given  in  the  following  table  :  — 


Name  of 
Disease 

From   Exposure 
till  First 
Symptoms 

Patient  is  Infectious 
to  Otheks 

Diphtheria 

2  days 

14  days  after  membrane  disappears. 

A  lumps 

10-22  days 

14  days  from  commencement. 

Scarlet  fever 

4  clays 

Until  all  scaling  has  ceased. 

Smallpox 

12-17  days 

Until  all  scabs  have  fallen. 

Measles 

14  days 

3   days    before    eruption    till    scaling 
and  cough  cease. 

Typhoid  fever 

1 1  days 

Until  diarrhoea  ceases. 

Whooping  cough 

14  days 

3  weeks  before    until  3    weeks  after 
beginning  to  whoop. 

Water  Supply.  —  Bacteria  are  more  abundant  in  flowing 
streams  than  in  water  standing  in  lakes  or  reservoirs  (con- 


BACTERIA   AND   SANITATION  163 

trary  to  the  usual  belief).  They  are  most  abundant  in 
rivers  that  flow  through  populous  regions.  They  are  com- 
paratively scarce  in  dry,  sandy  soils,  and  very  numerous  in 
moist,  loamy  soils.  The  water  of  cities  should  never  be 
taken  from  a  stream  or  lake  into  which  sewerage  flows 
unless  it  is  thoroughly  filtered.  Filters  are  constructed 
thus :  first  a  layer  of  small  stones,  next  a  layer  of  coarse 
sand,  lastly  a  layer  of  very  fine  sand  on  top,  the  total  thick- 
ness being  four  or  five  feet.  Beneficial  microbes  live  upon 
the  grains  of  sand  and  destroy  all,  or  nearly  all,  of  the 
dangerous  microbes  as  the  water  slowly  soaks  through. 
The  construction  of  such  waterworks  is  left  to  sanitary 
engineers,  of  course,  and  the  average  citizen  does  not  need 
to  know  the  details. 

The  department  of  street  cleaning  should  receive  the 
willing  cooperation  of  all  citizens.  Banana  peelings,  paper, 
etc.,  should  not  be  thrown  upon  the  street  or  school 
grounds.  Garbage,  ashes,  and  rubbish  should  be  placed  in 
separate  cans,  as  the  rules  provide.  Garbage  cans,  if  not 
thoroughly  cleaned,  acquire  unpleasant  odors  and  breed 
flies  and  bacteria.  They  should  be  thoroughly  washed 
with  very  hot  water  and  sal  soda  and  scalded  with  boiling 
water  and  scrubbed  with  an  old  broom.1 

The  chief  duties  of  the  Health  Department  are :  quar- 
antine isolation  and  disinfection,  with  the  purpose  of  pre- 
venting or  controlling  contagious  and  infectious  diseases  ; 

1  The  chief  Disinfectants  are  :  fresh  air,  sunshine,  heat,  formaldehyde,  etc. 
Airing  and  sunning  will  destroy  some  germs  in  bedding  and  clothing  as  effec- 
tually as  chemicals.  Boiling  and  steaming  are  the  best  ways  of  applying  heat. 
Formaldehyde  is  a  volatile  liquid.  After  room  is  sealed  and  strips  of  paper 
pasted  all  over  cracks,  a  specially  constructed  generator  is  applied  to  keyhole, 
and  room  kept  closed  for  12  hours.  Mercuric  chloride  (corrosive  sublimate) 
is  used  I  part  to  1000  parts  of  water  for  disinfecting  soiled  clothing,  towels, 
utensils,  surgeon's  instruments,  and  wounds.  In  place  of  this,  carbolic  acid, 
5  per  cent  solution,  may  be  used,  but  it  is  not  so  good  a  germicide. 


1 64  HUMAN  BIOLOGY 

inspection  of  dairies,  slaughterhouses,  and  other  sanitary 
work;  inspection  of  milk1  and  other  food  stuffs;  the  de- 
partment gathers  vital  statistics ;  it  enforces  the  rules  for 
disinfection  of  public  buildings. 

Importance  of  Cooperation  with  the  Health  Department.  - 
Only  an  ignorant  and  short-sighted  person  would  fail  to 
cooperate  promptly  and  cheerfully  with  local  or  state 
health  officers.  It  is  for  the  benefit  and  protection  of 
every  one  that  the  truth  concerning  contagious  diseases 
be  reported  promptly.  Only  in  this  way  may  outbreaks 
of  disease  be  prevented  and  many  lives  saved.  He  is  a 
bad  citizen  and  a  public  enemy  who  will  conceal  a  case  of 
disease  dangerous  to  the  community.  Outbreaks  of  fatal 
diseases  may  be  easily  prevented  or  stamped  out  if  the 
health  officer  is  sustained  and  his  directions  carried  out. 

1  Milk  may  be  sterilized  by  boiling,  but  boiled  milk  is  not  digestible  nor 
nutritious.  Milk  may  be  Pasteurized  by  immersing  bottles  of  milk  in  water 
which  is  kept  nearly  (but  not  quite)  at  boiling  point  (1600  F.)  for  five  min- 
utes. But  this  makes  the  milk  less  valuable  than  fresh  milk,  and  destroys 
beneficent  microbes.  Buttermilk  has  many  such  microbes,  which  kill  injurious 
microbes  and  purify  the  stomach.  Cleanliness,  or  an  aseptic  condition,  is  far 
preferable  to  antiseptics. 


INDEX 

I,  V,  X,  etc.  =  Introduction :    P  =  Plant  Biology :    A  =  Animal  Biology 
H  =  Human  Biology. 


Aboral  surface,  A  35. 

Aborted  seeds,  p  166. 

Absorption,  H  106. 

Abutilon,  p  156. 

Accessory  fruit,  P  164,  169. 

Accommodation  in  eye,  h  143,  153. 

Acephala,  A  107. 

Acid,  ix. 

Adaptation  to  environment,  p  6,  A  148, 
185,  201,  205,  207,  H  19,  108,  109, 
1 10. 

Adenoid  growths,  h  86. 

Adipose  tissue,  H  12. 

Adulteration  of  food,  H  93. 

Adventitious  roots,  p  36;    buds,  p  114. 

Aerial  roots,  P  34. 

Aggregate  fruit,  P  168. 

Air  cells,  h  75. 

Air  plants,  p  35. 

Akenes,  P  165. 

Albinism,  H  16,  18. 

Albumen,  H  92. 

Albumin,  H  92. 

Alcohol  and  circulation,  h  67 ;  and 
fermentation,  H  158;  and  food, 
H  113;  and  muscles,  H  50;  and 
nerves,  H  135;   and  skin,  H  20. 

Algar,  p  179,  183,  195. 

Alkaline,  ix. 

Alternation  of  generation,  P  179,  A  30, 

Ambulacral,  A  36. 

Ameba,  A  10. 

Americans,  H  1. 

Anadon,  A  98. 

Anatomy,  H  9. 

Anemophilous,  P  149. 

Animal  food,  H  95,  no. 

Annual  plant,  p  17. 

Antelope,  A  215. 

Antennae,  A  68,  87. 

Anther,  p  135,  144,  180. 

Antheridium,    P    178,    186,     198,    200, 

202,  203. 
Ant-eater,  giant,  a  199;   spiny,  A  196. 


Ant-lion,  A  91. 

Ape,  A  220. 

Apical  dehiscence,  p  166. 

Appendicitis,  h  106. 

Appendix,  vermiform,  H  106. 

Appetite,  H  94,  no. 

Aptera,  A  82. 

Apteryx,  A  174. 

Aquarium,  A  17. 

Archegonium,    p    178,    198,    200,    202, 

203. 
Argonaut,  paper,  a  107. 
Arm,  H  33. 
Armadillo,  A  200. 
Arrowhead,  H  2. 
Arteries,  H  51,  53,  54,  61. 
Arthropoda,  A  9,  125. 
Arum  family,  P  140. 
Ash,  p  92. 

Asiatic  cholera,  H  160. 
Assimilation,  p  97,  H  90. 
Association  fibers,  H  123,   126. 
Asthma,  H  86. 
Astigmatism,  H  144. 
Athletics,  H  46,  47. 
Atwater's  experiments,  H  113. 
Auricle,  H  53. 
Automatic  action,  h  123. 
Axil,  p  112. 
Axis,  plant,  P  15. 
Axon,  H  119. 

Bacillus,  H  158,  159. 

Bacteria,  p  39,   109,   182,  H  158,   159, 

160,  161. 
Bandage,  h  62. 
Barberry,  p  157,  193. 
Bark,  p  54,  66,  67. 
Bark-bound  trees,  p  54. 
Bast,  P  61,  66. 
Bat,  A  202. 
Baths,  H  23,  24. 
Batrachia,  A  126. 

Bean,  P  20,  28,  39,  194,  H  95,  96,  112. 
Beaver,  a  204. 


INDEX 


Bedbug,  A  92,  93. 

Bee,  bumble,  a  Sg;  honey,  a  88. 

Beebe's  experiments,  Dr.,  11  113. 

Beef,  H  1 1 1 ;  tea,  h  m. 

Beetle,  A  90,  91. 

Berry,  P  167. 

Biennial  plant,  P  17. 

Big-headed  turtle,  A   149. 

Bilateral,  A  34,  49,  98. 

Bile,  H  105. 

Bill  of  bird,  A  151. 

Biology  defined,  a  1,  h  9. 

Birds,  A  150. 

Blind  spot,  H  151. 

Blood,   h   58;    quantity   of,   H   55;    of 

insects,  A  78. 
Blood  vessels,  H  52;   control  of,  h  58. 
Board  of  Health,  H  163. 
Boll  weevil,  a  95,  96. 
Boll  worm,  A  95,  96. 
Bones,   H    29;    composition   of,    H   31; 

growth  of,  H  14,  36;    forms  of,  H  28, 

29,  34;    structure  of,  h  30. 
Bony  tissue,  h  13. 
Borax,  h  93. 
Brace  cells,  p  67. 
Bracts,  p  134. 
Brain,    h    122;     coverings    of,    h    125; 

of  fish,  A  118. 
Branch,  p  111,  a  9. 
Breathing,  forms  of,  h  80;    of  bird,  A 

161;   of  insect,  a  76;   through  mouth, 

H  85. 
Breeding,  plant,  p  7,  8. 
Bronchial  tubes,  H  75. 
Bruises,  H  62. 
Bryophytes,  P  181. 
Bud  propagation,  p  121. 
Budding,  p  127,  128. 
Buds,  p  72,  82,  87,  111;    flower,  p  115; 

fruit,  p  115. 
Bureau  of  entomology,  A  95. 
Burns,  H  24. 
Burs,  P  172,  174. 
Bushes,  P  191,  a  171. 
Butterfly,  a  83. 

Cabbage,  p  113,  h  95. 
Cabbage  butterfly,  a  84,  86,  87. 
Callus,  p  56. 
Calyx,  p  133. 
Cambium,  p  63,  65. 
Camel,  A  214. 
Candle,  xy,  A,  5. 
Cane  sugar,  h  92,  104. 
Capillaries,  h  52,  53,  56. 


Capsule,  p  165. 

Carbohydrate,  p  95,  h  91,  95. 

Carbon,  vii,  xviii,  p  92. 

Carbon,  dioxid,  a  24,  p  22,  93,  106, 
H  60,  76,  81,  132;    monoxid,  h  85. 

Carnivorous,  p  99,  h  hi, 

Carp,  a  112,  117,  123. 

Carpel,  p  136. 

Cartilage,  H  13,  35. 

Castor  bean,  p  24. 

Cat,  A  184. 

Caterpillar,  tent,  A  84. 

Catkin,  p  158. 

Caucasian,  h  i,  2. 

Caulicle,  p  20,  22,  25. 

Cedar  apple,  p  194. 

Cell,  p  42,  63,  145,  176,  A  6,  7,  h 
5,6. 

Celom,  A  46. 

Cephalopod,  a  106. 

Cerebellum,  H  122,  124. 

Cerebro-spinal  system,  H  128,  129. 

Cerebrum,  h  122,  125,  126. 

Chelonia,  a  143. 

Chemistry,  xv. 

Chemical  symbols,  xv. 

Chest,  H  32. 

Chewing,  H  90,  101. 

Chimpanzee,  A  219,  221. 

Chirping,  A  66. 

Chitin,  a  77. 

Chlorophyll,  P  86,  94,  101,  183,  186. 

Cholera,  H  160. 

Choroid,  H  150,  152. 

Chyme,  H  103. 

Cigarettes,  H  67,  86. 

Cilia,  a  14,  20,  101,  103,  h  76. 

Ciliated  chamber,  A  17. 

Cion,  p  125. 

Circulation,  h  51;  and  breathing,  h  58; 
and  exercise,  h  67  ;  hygiene  of,  H  68; 
in  ameba,  a  12;  in  insect,  A  77;  in 
fish,  a  117;  portal,  H  60,  105;  pul- 
monary, h  60;   renal,  h  60. 

City,  h  4. 

Cladophylla,  p  100. 

Clam,  hardshell,  A  104;  softshell, 
A  104. 

Class,  A  9. 

Classification,    of    animals,    A    8,    125; 
of    birds,    A     177;      insects,    A    82; 
mammals,  A  193. 
Cleft  graft,  p  126. 
Cleft  leaf,  p  75. 
Cleistogamous,  p  151. 
Click-beetle,  a  91. 


INDEX 


111 


Climate,  and  clothing,  h  25;  and  brain 
work,  11  68;   and  early  man,  h  2. 

Climbing  plants,  P  129. 

Clitellum,  A  43,  47. 

Cloaca,  a  18. 

Clot,  h  61. 

Clothes  moth,  A  84,  92,  93. 

Clothing,  H  16,  25. 

Clover,  p  39. 

Club  mosses,  P  203. 

Cluster,  flower,  P  155,  159;  centrif- 
ugal, p  156,  159;  centripetal,  p  156; 
indeterminate,  p  156. 

Coagulation,  H  61. 

Cockroach,  A  71. 

Cocoon,  a  84. 

Codling  moth,  A  84,  86,  87,  95. 

Ccelenterata,  A  28. 

Colds,  care  of,  H  69,  86. 

Coleoptera,  A  82. 

Collecting  insects,  A  72. 

Colon,  H  106,  in. 

Colonies,  plant,  P  11. 

Colorado  beetle,  A  90,  91. 

Coloration,  warning,  A  84,  146;  pro- 
tective, A  34,  37,  49. 

Colors  of  flowers,  A  85. 

Comparative  study,  A  85,  108,  122, 
223;    moth  and  butterfly,  A  85. 

Composite  flowers,  p  140. 

Compositions,  subjects  for,  h  15,  50, 
116,  141. 

Compound  substance,  vii. 

Congestion,  H  68. 

Conjugation,  p  185. 

Conjunctiva,  H  150. 

Connective  tissue,  H  n,  54,  120. 

Consumption,  H  159. 

Convolution,  h  126. 

Cooking,  H  1 14. 

Coordination,  H  124. 

Copper  head,  A  145. 

Coral,  A  31. 

Coralline,  A  31. 

Coral  snake,  A  145,  146. 

Cork,  p  66,  67. 

Corn,  p  3,  25,  26. 

Cornea,  H  150. 

Corolla,  P  133;  funnel  form,  P  138; 
labiate,  P  138;  personate,  P  139; 
rotate,    P   138  ;    salver  form,  p   138. 

Corpuscles,  origin  of,  H  30;  red,  H  59; 
white,  H  59,  60,  65,  68. 

Corset,  H  58,  80,  87. 

Cortex,  p  44. 

Corymb,  p  159. 


Cotton  plant,  P  7,  A  95.. 
Cotyledon,  p  20. 
Cricket,  A  71. 
Cross-fertilization,  A  25. 
Crowd  poison,  h  82. 
Cryptogam,  p  176,  1S0,  183-204. 
Cuckoo,  A  179. 
Currant,  p  157. 
Cuttings,  P  121,  123,  124. 
Cuttlefish,  A  107. 
Cyme,  p  159,  160. 
Cypraea,  A  104. 
Cysts,  A  13. 
Cytoplasm,  h  6. 

Darwin,  A  48,  148. 

Debates,  subjects  for,  H  141. 

Deciduous,  p  82. 

Decumbent,  p  50. 

Degeneration,  h  3,  4,  141. 

Dehiscence,  p  144,  164. 

Deliquescent,  p  51. 

Dendron,  H  119. 

Dependent  plants,  p  106. 

Dermis,  H  17. 

Devil's  horse,  A  71. 

De  Vries,  A  148,  224. 

Dextrin,  H  112. 

Diaphragm,  H  77,  78. 

Dichogamy,  P  144. 

Dicotyledon,  p  20. 

Dicotyledonous  stems,  p  61. 

Digestion,  p  95,  H  89,  96,  100. 

Digitate,  p  74. 

Digits,  A  222,  H  in. 

Dimorphous,  P  144. 

Dioecious,  P  138,  170. 

Diphtheria,  H  160. 

Diptera,  A  82. 

Disease,  defined,  h  5. 

Disinfection,  H  163. 

Dispersal  of  seeds,  p  172. 

Dissection,  p  30. 

Division  of  labor,  A  27,  29,  H  8. 

Dodder,  P  35,  106. 

Dog,  224. 

Dolphin,  a  209. 

Doodle  bug,  A  91. 

Dorsal,  A  43. 

Dove,  A  179. 

Dragon  fly,  a  93. 

Drainage,   H   158,    161. 

Dropsy,  H  64. 

Drugs,  H  60,  130,  133. 

Drupe,  p  168. 

Drupelet,  p  168. 


IV 


INDEX 


Duckbill,  a  196. 
Dust,  h  82,  158. 

Ear,   of  bird,   A    151;   of  frog,   A    131; 

of  fish,  A  112;   of  man,  H  154. 
Earthworm,  A  42. 
Echinodcrms,  A  9,  34,  125. 
Ecology,  p  14,  h  9. 
Economic  importance  of  birds,  A  167; 

insects,    A    93;      mollusks,    A     105; 

rodents,  A  206. 
Ectoderm,  A  26,  87. 
Ectoplasm,  A  11,  14. 

Egg,  of  insect,  A  81 ;  of  hen,  H95,  96,  112. 
Elaters,  p  198. 
Element,  viii. 
Embryo,  p  26,  180. 
Embryo  sac,  p  180. 
Enamel,  H  98. 
Endoderm,  a  26,  27,  37. 
Endodermis,  p  44. 
Endoplasm,  a  11,  14. 
Endosperm,  p  21,  24. 
Energy,  H  96,    140;    in   ameba,   A   12; 

organic,  A  2,  3 ;  plant,  A  2,  3,  5. 
Entomophilous,  p  148. 
Environment,  P  6,  A  148,  H  2,  3,  4,  48. 
Enzyme,  H  100. 
Epicotyl,  p  23,  25. 
Epidermis,  of  leaf,  p  86,  87;    of  man, 

h  17;    of  mussel,  A  98. 
Epigeal,  p  23. 
Epiphyte,  P  35,  no. 
Epithelial,  H  12,  54. 
Equisetums,  P  201. 
Erect  posture,  h  3. 
Esophagus,  H  74,  10 1. 
Essays,  subjects  for,  H  15,  25,  50,  116. 
Essential  organs,  p  135. 
Ethiopian,  H  12,  18. 
Evaporation,  viii. 
Excretion,  A  12. 
Excurrent,  P  51. 
Exercise,  H  45,  48,  49,  57,  67. 
Expiration,  H  79. 
Explosive  seeds,  p  172. 
Eye,  h  149;    of   bird,    a  159;    of  frog, 

A    30;     of    grasshopper,    A    67,    79; 

of  fish,  A   III. 

Fainting,  H  57. 
Family,  A  8. 

Fangs,  venomous,  A  145. 
Farmers'  bulletins,  A  95. 
Fatigue,  of  muscles,  H  45;    of  nerves, 
H  130,  131,  136. 


Fats,  test  for,  xi. 

Fatty  tissue,  H  12,  103. 

Feather,  A  155. 

Fehling's  solution,  xi. 

Ferment,  H  100,  103,  104,  158. 

Fermentation,  p  190,  h  158. 

Fern,  p  176. 

Fertilization,  p  144;  cross,  p  144,  146, 
A  85;    self,  p  145,  147,  188. 

Fiber,  h  2. 

Fibrin,  H  61. 

Fibro-vascular  bundles,  p  61,  90. 

Field  study,  p  3,  6,  8,  14,  19,  27,  46, 
57,  71,  84,  91,  101,  no,  118,  128, 
132,  143,  152,  162,  170,  174,  181, 
A  10,  22,  42,  71,  72,  97,  127,  165, 
166,  167,  184. 

Filament,  p  135. 

Filter,  h  163. 

Fins,  A  no,  113. 

Flagellum,  A  21,  27. 

Flatworm,  A  49. 

Flavors,  H  142,  147. 

Flea,  A  92,  93. 

Flight,  of  bird,  A  157,  175;  of  moth, 
A  84. 

Floral  envelopes,  p  133. 

Florets,  P  140. 

Flower,  p  133,  186,  A  85;  apetalous, 
p  136;  clusters,  P  155;  complete, 
P  136;  diclinous,  p  137;  double, 
p  142;  imperfect,  p  137;  incom- 
plete, p  136;  lateral,  p  136;  naked, 
P  136;  perfect,  P  137';  pistillate, 
P  137;  regular,  p  138;  staminate, 
p  137;  sterile,  p  137;  solitary,  p  156; 
terminal,  p  156. 

Fly,  horse,  A  Si ;   house,  A  92,  93. 

Foliage,  P  t6. 

Follicle,  P  165. 

Food,  H  88;  defined,  H  114;  of  birds, 
A  177. 

Food  stuffs,  h  91. 

Food  tube,  of  bird,  A  163 ;  of  fish,  A  1 16 ; 
of  insect,  a  76;  of  man,  h  97; 
of  mussel,  A  102. 

Foot,  h  29. 

Foraminifera,  a  15,  18. 

Forestry,  P  68. 

Formaldehyde,  h  163. 

Formalin,  H  93. 

Framework  of  plant,  P  15. 

Frog,  A  128. 

Frond,  p  176,  178,  181. 

Fruit,  P  163,  H  95. 

Fucus,  P  186. 


INDEX 


Funaria,  P  201. 

Function,  A  1,  H  9. 

Fungi,  p  187. 

Fungus,  p  107,  108,  184,  187,  195. 

Gametophyte,  p  179. 

Gamopetalous,  p  134. 

Gamosepalous,  p  134. 

Ganglion,  A  45,  H  120. 

Ganglionic  system,  H  127. 

Garbage,  h  163. 

Gasteropod,  A  108. 

Gastric  juice,  H  103. 

Gastrula,  A  7. 

General  sensation,  H  144,  145. 

Generation  of  plants,  p  16. 

Genus,  A  8. 

Geographical  barriers,  A  148. 

Geotropism,  p  44,  47. 

Germination,  P  22,  23,  27. 

Gila  monster,  A  147. 

Gills,  of    mussel,    A    100;     of    fish,    A 

US-      ■ 
Glands,  lymphatic,  h  65. 
Gland  tissue,  H  13. 
Glomerule,  p  160. 
Gnawing  mammals,  A  203. 
Gopher,  pouched,  a  204. 
Gorilla,  a  221. 
Grafting,  P  125. 
Grain,  H  95,  112. 
Grantia,  A  18. 
Grape  sugar,  x,  H  88,  92. 
Grasshopper,  A  70. 
Grit  cells,  P  67. 
Guard  cells,  p  88. 
Gullet,  H  74,  94,  101. 
Gymnastics,  H  47. 
Gymnosperm,  p  26,  170. 
Gypsy  moth,  A  95. 

Habit,  H  131. 

Hairs,  p  87,  H  19. 

Hands,  h  4;    defined,  A  220. 

Headaches,  H  132,   133. 

Heart,  human,  h  51,  52;  insect,   A   77; 

sound  of,  H  60. 
Heating,  H  84. 
Hemiptera,  A  82. 
Hemoglobin,  H  59,  81. 
Herb,  p  17. 

Heredity,  A  147,  153,  h  4. 
Hessian  fly,  A  95. 
Hill,  Dr.  L.  H.,  quoted,  H  140. 
Hilum,  p  21,  26. 
Hip,  H  4,  p  168. 


Hollyhock,  p  147. 

Homology,  p  135. 

Horned  toad,  A  140. 

Host,  p  107. 

House  fly,  A  92,  93. 

Houstonia,  p  107. 

Human  species,  H  1,  A  220. 

Hydra,  a  22. 

Hydranth,  A  29. 

Hydrochloric  acid,  H  103. 

Hydroid,  A  28,  29,  30. 

Hygiene,  H  49,  66,  80,  107,  129,  141. 

Hymenoptera,  A  82. 

Hypha?,  P  107,  188. 

Hypocotyl,  P  22. 

Hypogeal,  P  23. 

Hypostome,  A  23. 

Ichneumon  fly,  A  89. 
Imago,  A  81. 
Immunity,  H  158,  160. 
Indehiscent,  P  164. 
Indian,  H  2. 
Indusium,  p  177. 
Inflammation,  H  68,  86. 
Inflorescence,  P  155,  160. 
Infusoria,  A  16. 
Inhibit,  H  68. 
Inorganic,  A  1. 
Insecticides,  A  95. 

Insects,  a  73,  7s ;    biting,  a  82;    classi- 
fied, A  82;   sucking,  a  82. 
Inspiration,  H  77. 
Instinct,  A  80,  121;  h  49. 
Intercostal,  H  77. 
Internode,  P  52. 
Intestinal  gland,  H  104. 
Intestine,  H  98,  103,  106. 
Involucre,  p  34,   141,  163,   164. 
Iodine  test  for  starch,  x. 
Iris,  h  143,  151. 
Iron,  vii,  p  39. 
Iron  tonics,  H  90. 
Isoetes,  p  203. 
Ivory,  H  98. 

Jacana,  Mexican,  A  178. 
Jay,  blue,  a  181. 
Jelly  fish,  A  29,  30. 
Joints,  H  29,  35,  36. 

Kangaroo,  A  198. 
Key  fruit,  p  164. 
Kidneys,    of    fish,    a    117;     of   insects, 

A  76;    of  man,  h  26,  27;    of  mussel, 

A  102;   of  worm,  A  45. 


VI 


INDEX 


Kinctoscope,  H  151. 

Labial  palpi,  A  68,  74,  10 1. 
Labium,  a  68,  74. 

Laboratory,  p  3. 

Labrum,  A  68,  74. 

Labyrinth,  H  157. 

Lacteal,  H  64,  65,  104,  105. 

Lady  bug,  A  91. 

Lamellibranch,  A  107. 

Landscape,  I'  13. 

Lark,  meadow,  A  182;   sky,  A  179. 

Larkspur,  p  148,  149. 

Larva,  a  81. 

Larynx,  H  72. 

Lasso  cell,  a  34. 

Lateral  spinal  curvature,  H  37. 

Latex  tubes,  p  67. 

Leaf,   apex  of,   p   80;     base   of,   p   80; 

function  of,  P  92;    margin  of,  P  80; 

structure,  P  86. 
Leaf  scar,  p  90. 
Leaves,  arrangement  of,  p  82 ;    shapes 

of,  p  78,  85. 
Leg,  of  bird,  a  152;    of  horse,  A  210; 

of  insect,  A  74;    of  man,  H  33. 
Legume,  p  165,  h  95. 
Legume  family,  p  35,  169. 
Lemur,  A  220. 
Lenticel,  P  89. 
Lepidoptera,  A  82,  87. 
Lichens,  p  195. 
Ligneous,  p  17. 
Lime  water,  xx,  H  70. 
Liver,  H  105. 
Liverworts,  P  196. 
Lobes  of  leaf,  P  75. 
Lobule  of  lung,  h  75. 
Locule,  p  136,  163,  166. 
Loculicidal  dehiscence,  p  166. 
Louse,  A  92,  93. 
Lumber,  p  68. 

Lungs,  of  bird,  A  165;   of  man,  H  76. 
Lycopodium,  p  204. 
Lymph,  H  52,  62,  63. 
Lymphatics,  H  62,  63. 
Lymph  spaces,  h  63. 

Macrospore,  P  203,  204. 

Madreporite,  A  35. 

Malaria,  H  160. 

Malay,  h  i. 

Mammal,    a    184,    h    hi;     classified, 

A  193;    defined,  A  189. 
Manatee,  a  209. 
Mandibles,  A  68,  74. 


Mantis,  praying,  A  3. 

Mantle,  A  99. 

Marchantia,  p  196. 

M  axilla-,  A  68,  74. 

Maxillary  palpi,  a  68,  74. 

May  beetle,  A  90,  91. 

May  fly,  A  83. 

Measuring  worm,  A  81,  84. 

Medulla,  H  122,  123. 

Medullary  ray,  r  64. 

Medusa,  A  31. 

Mesoglea,  A  26. 

Mesophyll,  P  86. 

Metamorphosis  of  insect,  A  80,  81 
82. 

Metazoan,  A  1. 

Micropyle,  p  21,  26. 

Microscope,  p  21,  26. 

Microspore,  P  203. 

Midrib,  p  77. 

Migration  of  birds,  A  171,  173. 

Milk,  H  91,  95,  96,  112. 

Mimicry,  A  146. 

Mind  and  health,  h  129. 

Minerals,  xiv,  h  90,  91,  93,  95. 

Mint  family,  p  139. 

Mistletoe,  P  109. 

Moccasin,  a  145. 

Mold.sP  188. 

Mole,  A  201. 

Mollusk,  A  9,  97,  125. 

Molting, Sa  69,  174.  - 

Mongolian,  h  i. 

Monkey,  A  220. 

Monocotyledons,  P   20,   25,  63. 

Monoecious,  P  138,  150,  170. 

Morphine,  H  105. 

Morula,  A  7. 

Mosquito,  A  92,  93,  96,  H  160,  161. 

Mosses,  p  199. 

Moss,  Spanish,  p  no. 

Moth,  A  83. 

Mother-of-pearl,  a  99. 

Motor,  cell,  H  120;   fiber,  h  120. 

Mullein,  p  87. 

Municipal  sanitation,   h   162,   163. 

Muscadine,  P  36. 

Muscles,  H  39 ;  arrangement  of, 
H  41;  control  of,  H  39,  44;  function 
of,  H  39,  43;  growth,  H  42;  kinds 
of,  H  39;    structure  of,  H  39. 

Muscles  and  health,  H  45. 

Muscular  sense,  H  142,  146. 

Muscular  tissue,  H  1 1. 

Mushroom,  p  107,  194. 

Mussel,  A  96,  103. 


INDEX 


Vll 


Mycelium,  P  107,  108,  188. 
Mychorrhiza,  P  108. 

Nails,  H  iq. 

Narcotic,  h  137,  14S. 

Nasal  tone,  h  144. 

Natural  selection,  P  8,  A  148. 

Nautilus,  chambered,  A  107. 

Nectar,  A  8,  P  148. 

Nephridium,  A  45. 

Nerve,  H  119;    spinal,  H  127;    cranial, 

H  127. 
Nerve  cell,  H   119;    fatigue  of,  H   130. 
Nerve  center,  H  117,  120. 
Nerve  fiber,  H  119. 
Nerve  tissue,  H  11. 
Nerves,  vasomotor,  H  23. 
Nervous  children,  H  135. 
Nervous  system,  of  bee,  A  78;    of  man, 

±7  117;    of  mussel,  a  102. 
Nest  building,  A  166,  182. 
Neuron,  H  118. 
Neuroptera,  A  82. 
Neutral  substances,  ix. 
Nitella.  p  187. 

Nitric  acid  test  for  proteid,  xi. 
Nitrogen,  viii,  p  39,  40,  h  81. 
Nitrogenous  compounds,  xi. 
Nodes,  p  20,  52. 
Nodules,  p  39,  40. 
Nose  bleed,  h  52. 
Nostoc,  p  184. 

Nostril,  of  bird,  A  151;   of  fish,  A  112. 
Notebooks,  P  3. 
Nucleolus,  A  6,  h  6. 
Nucleoplasm,  H  7. 
Nucleus,    p    144,    185,    a    6,    11,    14, 

H  6,  18. 
Nutrients,  H  91. 
Nuts,  p  164,  h  95. 

Octopus,  a  106. 
Oil  gland,  H  20. 
Oils,  test  for,  xi. 
Okapi,  A  214. 
Oleander,  p  86. 
Omnivorous,  A  47,  Em. 
One-celled  animals,  A  7. 
Oogonia,  p  186. 
Opossum,  a  197;    H  4. 
Opsonin,  h  162. 
Optic  nerve,  h  151,   152. 
Oral  surface,  A  35. 
Orang,  A  227. 
Orbit,  H  149. 
Orchid,  p  35,  no. 


Order,  A  9. 

Organ,  A  1,  H  9. 

Organic,  xiv,  A  1. 

Organism,  A  1. 

Orthoptera,  A  82. 

Oscillatoria,  p  184. 

Osculum,  A  18. 

Osier,  Dr.  William,  quoted,  H  133. 

Osmosis,  P  42,  48. 

Outdoor  life,  H  5,  22. 

Ovary,    p    135,    144.    163,    170,    A    25 

37.  "7- 

Overgrowth,  P  12. 

Oviduct,  A  46. 

Ovule,  P  144,  186. 

Oxidation,    xii,    A    3,    4,    5,    H    14,    90, 

91,  120. 
Oxygen,  viii,  a  4,  5,  h  4,  76,  81,  140. 
Oyster,  A  104. 

Palisade  cells,  P  86. 

Palmate,  p  74. 

Pancreas,  H  104. 

Panicle,  P  158. 

Papilla,  H  17. 

Pappus,  P  141. 

Parameciurn^^&^i^y 

Parasites,  p  107,  a  49,  93. 

Parenchyma,  P  6o,  86. 

Partridge,  a  178. 

Pearls,  a  105. 

Peccary,  A  217. 

Pedicel,  P  162. 

Peduncle,  P  62. 

Peltate,  P  77. 

Pelvis,  H  33. 

Pepsin,  H  103. 

Perch,  A  109,  no,  123. 

Perennial,  P  17. 

Pericarp,  p  164,  165,  169. 

Peristalsis,  H  102,  106,  127. 

Peritoneum,  H  106. 

Pests,  insect,  A  93. 

Petals,  P  134. 

Petiole,  p  76 

Phagocyte,  H  161. 

Pharynx,  H  73,  85,  10 1. 

Pheasant,  A  174. 

Phenogam,  p  177,  180. 

Phosphorus,  vi. 

Photo-synthesis,  P  94,  10 1. 

Phyllotaxy,  P  84. 

Physics,  xiv. 

Physiology,  H  9. 

Pigment,  H  18. 

Pine  cone,  p  27,  170. 


INDEX 


Pinna,  p  1X1. 

Pinnate,  P  74. 

Pinnatifid,  p  76. 

Pistil,  p  135. 

Plantain,  p  157. 

Plant  societies,  p  g. 

Plants,  unlikencss  of,  P  9. 

Plastron,  A  14  1. 

Pleura,  h  76. 

Plexus,  H  128. 

Plumule,  P  20,  23,  25. 

Plur-annual,  P  18. 

Pod,  p  164. 

Poison,  H  137. 

Pollen,  p  135,  144,  180,  A  85. 

Pollen  basket,  A  88. 

Pollination,  p  144,  145;  artificial,  p 

Polyp,  a  9,  22,   125. 

Polypetalous,  p  134. 

Polysepalous,  P  134. 

Polytrichum,  p  199. 

Pome,  p  169. 

Portal  vein,  H  105. 

Portuguese  man-o'-war,  A  28. 

Posterior  curvature  of  spine,  H  37. 

Potato,  H  92,  95,  112;   bug,  A  90. 

Practical  questions,  H  50,  69,  87, 

136. 
Primates,  A  220. 
Primitive  man,  H  3. 
Primrose,  p  149. 
Proboscis,     of     butterfly,     A     83, 

elephant,  A  207. 
Prolegs,  A  84,  87. 
Propagation  by  buds,  P  121. 
Prop-roots,  P  36. 
Protection  of  birds,  A  171. 
Protective  resemblance,  a  34,  146. 
Proteid,  xi,  H  88,  91,  92,  94,  95,  96, 
Proterandrous,  p  146. 
Proterogynous,  p  146. 
Prothallus,  p  178,  202. 
Protoplasm,    xiv,    P    42,     94,    97, 

A  6,  11,  H  5,  6,  59,  106,  118. 
Protozoa,  A  7,  9,  11,  125. 
Pruning,  p  105. 
Pseud-annual,  P  17. 
Pseudoneuroptera,  A  82. 
Pseudopod,  A  i  i. 
Pteridophytes,  p  181,  201,  203. 
Ptyalin,  H  100. 
Puffball,  p  iQ4. 
Pulse,  H  55. 
Pure  food  law,  h  93. 
Pylorus,  H  103. 
Pyxis,  P  166. 


153- 


87; 


185, 


Quarantine,  H  163. 
Quarter-sawed,  P  70. 
Quill,  A  156. 

Rabbit,  A  205,  223. 

Radial  symmetry,  a  34,  125. 

Ration,  daily,  H  94,  96. 

Rattlesnake,  a  145. 

Reaction,  h  151,  152. 

Receptacle,  p  134,  163. 

Rectum,  A   134,  H  97. 

Reflex  action,  h  121. 

Regeneration  of  lost  parts,  A  37. 

Rennin,  H  103. 

Reproduction,    A    12,    15,    20,    25,   37, 

46,  120. 
Reptiles,  A  139. 
XBespiration,    cellular,    H    81;     human, 

H  70;    hygiene  of,  H  807    in  plants, 

p  97,  103. 
Resting   spore,    p    184,    185,    189,    191, 

192. 
Retina,  H  151,  152. 
Rhizome,  p  52,  202. 
Rhizopoda,  A  16. 
Road  runner,  A  169. 
Robin,  A  183. 
Root  cap,  p  44. 
Root  climber,  p  129. 
Root  hairs,  p  41,  42,  46. 
Rootlet,  p  41. 
Root  pressure,  P  99,  104. 
Roots,  and  air,  p  41;    forms  of,  P  32; 

function,  p  38;    structure,  P  38,  43; 

systems,  p  32. 
Rotifer,  A  49. 
Round  worm,  A  49. 
Ruminant,  A  213. 
Rust,  P  192. 

Salamander,  A  134,  138,  139. 

Saliva,  H  96,  100,  112. 

Salt,  x,  H  93. 

Samara,  p  164. 

Sand,  xiii. 

Sandworm,  A  49.  . 

Sanitary  map,  H  158. 

San  Jose  scale,  A  95. 

Sap,  p  67. 

Saprophyte,  P  107,  108. 

Scab  in  sheep,  A  93. 

Scales,   of   bird,   A    161;     fish,   A    no; 

moth,  A  89. 
Scallops,  a  104. 
Scape,  p  161. 
Scarab,  a  90,  91. 


INDEX 


IX 


School  and  health,  H  135. 

Sclerotic,  H  150. 

Scouring  rush,  P  203. 

Scramblers,  p  129. 

Sea  anemone,  A  33. 

Sea  fan,  A  32. 

Sea  horse,  A  124. 

Sea  urchin,  A  38. 

Seed,  p  20,  163,  180;   coat,  p  21. 

Selaginella,  P  204. 

Selection,  natural,  P  8;   artificial,  p  8. 

Sense,     muscular,     H     143;      thermic, 

h  142. 
Senses  of  insects,  A  76. 
Sensory,    cell,    H    120;    fiber,    H    120, 

121. 

Sepal,  p  133,  169. 

Septicidal  capsule,  p  166. 

Serum,  h  61. 

Sessile,  p  77. 

Seta?,  a  43,  48. 

Sexual  selection,  A  174. 

Shark,  A  121. 

Shelf  fungus,  P  194. 

Shoes,  h  48. 

Shoulder,  h  32. 

Shrub,  p  19. 

Sick  headache,  H   133. 

Sieve  tubes,  p  66. 

Silicle,  p  167. 

Silique,  P  167. 

Silkworm,  A  84,  86,  95. 

Silver  scale,  A  83. 

Siphon,  a  10 1. 

Siphonoptera,  a  82. 

Skeleton,  of  bird,  A   152;    cat,  A   188; 

frog,   A    131;    of  fish,   A    113;     man, 

H  28;    chart  of,  A  218. 
Skin,  H  16. 

Skull,  H  63;   mammalian,  A  194. 
Sleep,  H  130. 
Slipper  animalcule,  A  13. 
Sloth,  A  199. 
Slug,  A  105. 
Smell,  H  147. 
Snail,  A  105. 
Societies,  p  9. 
Soil,  p  40,  47,  A  48. 
Soredia,  p  196. 
Sori,  p  177,  192. 
Souring  of  milk,  H  158. 
Spadix,  P  140. 

Sparrow,  A  182;    English,  A  170. 
Spathe,  P  138,  140. 
Specialization,     A     20,     27,     66,     210, 

H  8. 


Species,  A  8. 

Spermary,  A  25,  27. 

Spermatophytes,  P  180. 

Spicule,  A  18. 

Spider,  A  94. 

Spike,  P  157. 

Spinal  cord,  H  120,  121. 

Spinal  deformities,  H  37. 

Spine,  H  31. 

Spiracle,  A  77,  87. 

Spirogyra,  P  184. 

Sponges,  A  17,  125;   glass,  A  19;   horny, 
A  19;   limy,  a  19. 

Spontaneous  combustion,  xiii. 

Sporangium,    p     177,     186,     188,    201, 
203,  204. 

Spore,  p  176,  178,  181,  184,  H  159. 

Sporophyll,  P  180,  201. 

Sporophyte,  P  177. 

Sports,  A  148,  224. 

Sprain,  H  38. 

Squash  bug,  A  93,  95. 

Squid,  A  106. 

Stamen,  P  135. 

Starch,  x,  p  95,  101,  H  88,  91. 

Starvation,  H  138. 

Stem,  P  49 ;   endogenous,  P   59 ;   exoge- 
nous, p  61;   kinds  of,  p  49. 

Sterilizing  wounds,  H  163. 

Stickleback,  A  119. 

Stigma,  p  135,  144,  145- 

Stimulant  defined,  H  137. 

Stipule,  P  76,  84. 

Stock,  P  125. 

Stomate,  p  87. 

Stone  age,  h  2. 

Stone  fruit,  p  168. 

Storage  of  food,  p  99. 

Street  cleaning,  h  163 

Struggle  to  live,  P  4,  6,  A  147,  H  4 

Study,  comparative,  A  82,   149,  223 

Style,  p  135,  163. 

Sugar,  H  91,  100. 

Sulphur,  vii. 

Summer-spore,  P  191. 

Sun  energy,  P  95,  A  2,  H  91. 

Sunlight,  A  2,  H  18. 

Survival    of   fittest,    P    7,    A    147,    H    4 
141. 

Sutures,  H  35. 

Swarm-spores,  P  186. 
Sweat  gland,  H  20. 
Symbiosis,  P  196. 
Sympathetic  system,  H  127,  129. 
Syngenesious,  p  141. 
Synovial  fluid,  H  36. 


INDEX 


1  adpole,  a  1 26,  134. 
Tanner,  Dr.,  H  138. 
Tapeworm,  a  49. 

Tarantula,  A  94. 

Taste,  h  no,  14.;,  146. 

Tear  gland,  H  149. 

Teeth,  h  88,  98,  99,  in;  of  frog, 
A   130. 

Teleutospores,  192. 

Temperature,  H  si;  nerves  of,  H  \\2, 
146. 

Tendon,  H  41. 

Tendril,  P  101. 

Terrapin,  A  143,  144. 

Thallophyte,  p  181,  184. 

Thallus,  P  184,  197. 

Thompson,  Sir  Henry,  on  smoking, 
H  87. 

Thoracic  duct,  H  64,  65,   105. 

Thorns,  P  101. 

Thought  questions,  h  20,  27,  79,  107, 
109,  116. 

Thvrse,  P  160. 

Thyroid  gland,  H  97. 

Tillandsia,  P  1 10. 

Timber,  decay  of,  P  195. 

Tissue,  H  7,  10,  p  60,  62. 

Toad,  A  137. 

Toadstool,  p  194. 

Tobacco,  and  heart,  H  67;  and  lungs', 
H  86;  and  taste,  h  148;  when  enjoy- 
able, h  87. 

Tortoise,  A  140,  143,  144. 

Torus,  p  134,  169. 

Touch,  H  145,  A  119. 

Toxin,  H  160,  161. 

Toyi    Niku,   Madame,   quoted,   H    141. 

Trachea,  H  74. 

Tracheid,  P  65. 

Transpiration,  P  98,  103. 

Trap-door  spider,  A  94. 

Tube  feet,  A  35. 

Tuberculosis,  H  5,  160. 

Tumble  bug,  A  90,  91. 

Turtle,  A    140,    143,    144. 

Twiners,  P  129,   131. 

Typhoid  fever,  H   159. 


Umbel,  P  159. 
Umbo,  A  98. 
Undergrowth,  P  12. 
Ungulate,  A  212. 
Urea,  H  94. 
Uric  acid,  H  114. 
Urinary  tubule,  h 


Vacuole,  A  n,  12,  14. 

Valve,  p  164,  h  51,  S3,  57. 

Vampire,  A  203. 

Variation,  A   147,  p  2. 

Variety,  a  8. 

Vaso-motor  nerves,  H  23,  68. 

Vaucheria,  p  186. 

Vegetables,  H  95,   112. 

Venomous  snakes,  A  143. 

Vent,  a  42. 

Ventilation,  h  71,  82,  83. 

Ventral,  A  43. 

Ventricle,  H  53. 

Vermes,  a  9,  125. 

Vermiform  appendix,  H  4,  106. 

Vertebra,  H  71,  82,  83. 

Vertebrates,  A  9,  125. 

Vertebrate  skeletons,  A  218. 

Verticellate,  p  84. 

Vestigial  organs,  H  106. 

Villi,  h  104. 

Vinegar,  h  94. 

Viscera,  H  127;   of  bird,  A  163. 

Vitreous  humor,  H  132. 

Voluntary  act,  H  122,  124. 

Warning  sound,  A  147. 

Wasps,  digging,  A  89. 

Water-pore,  P  88. 

Waterworks,  H  163. 

Weevil,  A  90,  91,  96. 

Whale,  A  208. 

Wheat  rust,  P  192. 

White    corpuscles,    H    59 ;      origin    of, 

H  61 ;   work  of,  H  60,  161,  162. 
White  weed,  or  ox-eye  daisy,  P  155. 
Whorled,  p  84. 
Willow  mildew,  p  190. 
Wind  travelers,  P  173. 
Wings,  of  grasshopper,  A  67;    of  bird, 

A  iS3.  158. 
Woodpecker,  A  180. 
Woody  fiber,  P  1*. 
Worms,  A  42. 
Wounds  of  plants,  P  56. 
Written  exercises,  H  15,  50,  116. 

Yeast  plants,  P  190,  H  158. 
Yellow  fever,  H  160. 
Yellow  spot,  H  151. 

Zoology  defined,  A  1. 
Zoophytes,  A  33. 
,-gnema,  p  185. 
;ospore,  p  185,  189,  181,  189. 


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really  more  serviceable  than  the  manikins  usually  found  in 
schools.  This  book  contains  twenty-five  Thought  Lessons 
of  about  ten  questions  each,  logically  developing  different 
lines  of  thought ;  also  three  hundred  questions  in  Applied 
Physiology. 


THE    MACMILLAN    COMPANY 

Sixty-four    and    Sixty-six    Fifth    Avenue,    New    York 


BOTANY 

An  Elementary  Text  for  Schools.  By  L.  II.  Bah  i  v,  I  >irector  of  the  Col- 
lege of  Agriculture,  and  Professor  of  Rural  Economy  in  Cornell 
University.  Revised  and  enlarged.  Illustrated.  i2mo.  Half 
leather,     xiv  +  355  pages.     $1.10  net. 

The  subjects  treated  are  four  in  number :  the  nature  of  the 
plant  itself,  the  relation  of  the  plant  to  its  surroundings,  the 
minute  structures  of  plants,  and  the  determination  of  the  kinds 
of  plants.  Each  of  these  subjects  is  practically  distinct,  so  that 
the  teacher  may  begin  where  he  will. 

The  five  hundred  illustrations  in  the  book  are  an  important 
as  well  as  an  attractive  feature.  They  are  not  pictures  merely 
—  they  are  illustrations  of  the  subject-matter ;  many  of  them 
are  reproductions  of  photographs. 

A  flora  containing  descriptions  of  more  than  six  hundred 
common  wild  and  cultivated  plants,  with  keys  to  the  natural 
orders,  completes  the  book. 


LESSONS  WITH  PLANTS 

Suggestions  for  Seeing  and  Interpreting  Some  of  the  Common  Forms  of 
Vegetation.  By  Professor  L.  II.  Bailey.  Illustrated.  i2mo. 
Half  leather,     xxxi  +  491  pages.     #1.10  net. 

The  book  is  based  upon  the  idea  that  the  proper  way  to 
begin  the  study  of  plants  is  by  means  of  plants,  instead  of 
formal  ideas  or  definitions.  Instead  of  a  definition  as  a  model 
telling  the  pupil  what  he  is  to  see,  the  plant  shows  him  what 
there  is  to  be  seen,  and  the  definition  follows.  In  this  way  the 
pupil  soon  begins  to  generalize,  and  the  conclusion  reached  is 
the  true  definition. 


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Sixty-four    and    Sixty-six    Fifth    Avenue,    New    York 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 

AN  INITIAL  FINE  OF  25  CENTS 

WILL   BE   ASSESSED    FOR    FAILURE  TO    RETURN 
THIS    BOOK   ON    THE    DATE   DUE.    THE   PENALTY 
WILL  INCREASE  TO  50  CENTS  ON  THE  FOURTH 
DAY     AND     TO     $I.OO     ON     THE     SEVENTH     DAY 
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Vn  J?J®H 

I  LMMY 

sth  *  9  1935 

flpn     o    C      IQci 

Arh    c  u    lyol 

OCT  "SIB  1968  \\ 

- 

LD  21-100m-8,'34 

u/ 


